When would one actually want to use a market order instead of a limit order?
If you have $10000 and wish to buy 1000 shares of a $10 stock, you risk borrowing on margin if you go over a bit. For some people, that's a non-issue. Some folk with an account worth say, $250K don't mind going over now and then or even let the margin account run $100K on a regular basis.  But your question is about market orders. A limit order above the market price will fast-fill at the market anyway. When I buy a stock, it's longer term usually. A dime on a $30 share price won't affect my buy decision, so market is ok for me. You put in a market order when you want to sell to whomever raises their hand first.  It results in the fastest possible liquidation of your stock. It's appropriate when you need to sell now, regardless of price. An example of when to use it: It's 3:55 PM, the market's going to close in 5 minutes and you need to sell some stocks to make some kind of urgent payment elsewhere.  If instead you have a limit order in place, you might not reach the limit price before the market closes, and you'll still own the stock, which might not be what you want. Firstly what are you trading that you could lose more than you put in? If you are simply trading stocks you will not lose more than you put in, unless you are trading on margin. A limit order is basically that, a limit on the maximum price you want your buy order bought at or the minimum price you want your sell order sold at. If you can't be glued to the screen all day when you place a limit order, and the market moves the opposite way, you may miss out on your order being executed. Even if you can be in front of the screen all day, you then have to decide if you want to chase the market of miss out on your purchase or sale. For example, if a stock is trading at $10.10 and you put a limit buy order to buy 1000 shares at or below $10.00 and the price keeps moving up to $10.20, then $10.30 and then $10.50, until it closes the day at $11.00. You then have the choice during the day to miss out on buying the shares or to increase your limit order in order to buy at a higher price. Sometime if the stock is not very liquid, i.e. it does not trade very often and has low volume, the price may hit $10.00 and you may only have part of your order executed, say 500 out of your 1000 shares were bought. This may mean that you may have to increase the price of your remaining order or be happy with only buying 500 shares instead of 1000. The same can happen when you are selling (but in reverse obviously). With market order, however, you are placing a buy order to buy at the next bid price in the depth or a sell order to sell at the next offer price in the depth. See the market depth table below:  Note that this price depth table is taken before market open so it seems that the stock is somewhat illiquid with a large gap between the first and second prices in the buyers (bid) prices. When the market opened this gap is closed, as WBC is a major Australian bank and is quite liquid. (the table is for demonstration purposes only). If we pretend that the market was currently open and saw the current market depth for WBC as above, you could decide to place a limit sell order to sell 1000 shares at say $29.91. You would sell 100 shares straight away but your remaining 900 sell order will remain at the top of the Sellers list. If other Buyers come in at $29.91 you may get your whole sale completed, however, if no other Buyers place orders above $29.80 and other Sellers come into the market with sell orders below $29.91, your remaining order may never be executed. If instead you placed a market sell order you would immediately sell 100 shares at $29.91 and the remaining 900 shares at $29.80. (so you would be $99 or just over 0.3% worse off than if you were able to sell the full 1000 shares at $29.91). The question is how low would you have had to lower your limit order price if the price for WBC kept on falling and you had to sell that day? There are risks with whichever type of order you use. You need to determine what the purpose of your order is. Is it to get in or out of the market as soon as possible with the possibility of giving a little bit back to the market? Or is it to get the price you want no matter how long it takes you? That is you are willing to miss out on buying the shares (can miss out on a good buy if the price keeps rising for weeks or months or even years) or you are willing to miss out on selling them right now and can wait for the price to come back up to the price you were willing to sell at (where you may miss out on selling the shares at a good price and they keep on falling and you give back all your profits and more). Just before the onset of the GFC I sold some shares (which I had bought a few years earlier at $3.40) through a market order for $5.96. It had traded just above $6 a few days earlier, but if instead of a market order I had placed a limit order to sell at $6.00 or more I would have missed out on the sale. The price never went back up  to $6 or above, and the following week it started dropping very quickly. It is now trading at about $1.30 and has never gone back above $2.00 (5.5 years later). So to me placing a limit order in this case was very risky. "After learning about things that happened in the ""flash crash"" I always use limit orders. In an extremely rare instance if you place a market order when there is a some glitch, for example some large trader adds a zero at the end of their volume, you could get an awful price.  If I want to buy at the market price, I just set the limit about 1% above the market price. If I want to sell, I set the limit 1% below the market price. I should point out that your trade is not executed at the limit price. If your limit price on a buy order is higher than the lowest offer, you still get filled at the lowest offer. If before your order is submitted someone fills all offers up to your limit price, you will get your limit price. If someone, perhaps by accident, fills all orders up to twice your limit price, you won't end up making the purchase. I have executed many purchases this way and never been filled at my limit price."
There are a couple of things you could do, but it may depend partly on the type of orders your broker has available to you. Firstly, if you are putting your limit order the night before after close of market at the top of the bids, you may be risking missing out if bid & offer prices increase by the time the market opens the next day. On the other hand, if bid & offer prices fall at the open of the next day you should get your order filled at or below your limit price. Secondly, you could be available at the market open to see if prices are going up or down and then work out the price you want to buy at then and work out the quantity you can buy at that price. I personally don't like this method because you usually get too emotional, start chasing the market if prices start rising, or start regretting buying at a price and prices fall straight afterwards. My preferred method is this third option. If your broker provides stop orders you can use these to both get into and out of the market. How they work when trying to get into the market is that once you have done your analysis and picked a price that you would want to purchase at, you put a stop buy order in. For example, the price closed at $9.90 the previous day and there has been resistance at $10.00, so you would put a stop buy trigger if the price goes over $10, say $10.01. If your stop buy order gets triggered you can have either a buy market order or a limit order above $10.01 (say $10.02). The market order would go through immediately whilst the limit order would only go through if the price continues going to $10.02 or above. The advantage of this is that you don't get emotional trying to buy your securities whilst sitting in front of the screen, you do your analysis and set your prices whilst the market is closed, you only buy when the security is rising (not falling). As your aim is to be in long term you shouldn't be concerned about buying a little bit higher than the previous days close. On the other hand if you try and buy when the price is falling you don't know when it will stop falling. It is better to buy when the price shows signs of rising rather than falling (always follow the trend). "One practical application would be to protect yourself from a ""flash crash"" type scenario where a stock suddenly plunges down to a penny due to transient market glitches. If you had a stop-loss order that executed at a penny (for a non-penny stock) it would be probably be voided by the exchange, but you might not want to take that risk." "What you are saying is a very valid concern.  After the flash crash many institutions in the US replaced ""true market orders"" (where tag 40=1 and has no price) with deep in the money limit orders under the hood, after the CFTC-SEC joint advisory commission raised concerns about the use of market orders in the case of large HFT traders, and concerns on the lack of liquidity that caused market orders that found no limit orders to execute on the other side of the trade, driving the prices of blue chip stocks into the pennies.  We also applaud the CFTC requesting comment regarding whether it is   appropriate to restrict large order execution design that results in   disruptive trading. In particular, we believe there are questions   whether it is ever appropriate to permit large order algorithms that   employ unlimited use of market orders or that permit executions at   prices which are a dramatic percentage below the present market price   without a pause for human review So although you still see a market order on the front end, it is transformed to a very aggressive limit in the back end. However, doing this change manually, by selling at price 0 or buying at 9999 may backfire since it may trigger fat finger checks and prevent your order from reaching the market.  For example BATS Exchange  rejects orders that are priced too aggressively and don't comply with the range of valid prices.  If you want your trade to execute right now and you are willing to take slippage in order to get fast execution, sending a market order is still the best alternative." The price is moving higher so by the time you enter your order and press buy, a new buyer has already come in at that time and taken out the lowest ask price. So you end up chasing the market as the prices keep moving higher. The solution: if you really want to be sure that you buy it and don't want to keep chasing the market higher and higher, you should put in a market order instead of a limit order. With a market order you may pay a few cents higher than the last traded price but you will be sure to have your order filled. If you keep placing limit orders you may miss out altogether, especially if the price keeps moving higher and higher. In a fast moving market a market order is always best if your aim is to be certain to buy the stock. "A market sell order will be filled at the highest current ""bid"" price. For a reasonably liquid stock, there will be several buy orders in line, and the highest bid must be filled first, so there should a very short time between when you place the order and when it is filled.   What could happen is what's called front running. That's when the broker places their own order in front of yours to fulfill the current bid, selling their own stock at the slightly higher price, causing your sale to be filled at a lower price.  This is not only unethical but illegal as well. It is not something you should be concerned about with a large broker.   You should only place a market order when you don't care about minute differences between the current ask and your execution price, but want to guarantee order execution. If you absolutely have to sell at a minimum price, then a limit order is more appropriate, but you run the risk that your limit will not be reached and your order will not be filled. So the risk is a tradeoff between a guaranteed price and a guaranteed execution." Limit orders are generally safer than market orders. Market orders take whatever most-favorable price is being offered. This can be especially dangerous in highly volatile stocks which have a significant spread between the bid and ask. That being said, you want to be very careful that you enter the price you intend into a limit order. It is better to be a bit slower at entering your orders than it is to make a terrible mistake like the one you mention in your question. If you can afford the cost and risk of 100 shares of stock, then just sell a put option.  If you can only afford a few shares, you can still use the information the options market is trying to give you -- see below. A standing limit order to buy a stock is essentially a synthetic short put option position. [1]  So deciding on a stock limit order price is the same as valuing an option on that stock. Options (and standing limit orders) are hard to value, and the generally accepted math for doing so -- the Black-Scholes-Merton framework -- is also generally accepted to be wrong, because of black swans. So rather than calculate a stock buy limit price yourself, it's simpler to just sell a put at the put's own midpoint price, accepting the market's best estimate. Options market makers' whole job (and the purpose of the open market) is price discovery, so it's easier to let them fight it out over what price options should really be trading at. The result of that fight is valuable information -- use it. Sell a 1-month ATM put option every month until you get exercised, after which time you'll own 100 shares of stock, purchased at: This will typically give you a much better cost basis (several dollars better) versus buying the stock at spot, and it offloads the valuation math onto the options market.  Meanwhile you get to keep the cash from the options premiums as well. Disclaimer: Markets do make mistakes.  You will lose money when the stock drops more than the option market's own estimate. If you can't afford 100 shares, or for some reason still want to be in the business of creating synthetic options from pure stock limit orders, then you could maybe play around with setting your stock purchase bid price to (approximately): See your statistics book for how to set ndev -- 1 standard deviation gives you a 30% chance of a fill, 2 gives you a 5% chance, etc. Disclaimer: The above math probably has mistakes; do your own work.  It's somewhat invalid anyway, because stock prices don't follow a normal curve, so standard deviations don't really mean a whole lot.  This is where market makers earn their keep (or not). If you still want to create synthetic options using stock limit orders, you might be able to get the options market to do more of the math for you. Try setting your stock limit order bid equal to something like this: Where put_strike is the strike price of a put option for the equity you're trading.  Which option expiration and strike you use for put_strike depends on your desired time horizon and desired fill probability.  To get probability, you can look at the delta for a given option.  The relationship between option delta and equity limit order probability of fill is approximately: Disclaimer: There may be math errors here.  Again, do your own work. Also, while this method assumes option markets provide good estimates, see above disclaimer about the markets making mistakes. In simple terms, this is how the shares are traded, however most of the times market orders are placed. Consider below scenario( hypothetical scenario, there are just 2 traders) Buyer is ready to buy 10 shares @ 5$ and seller is ready to sell 10 shares @ 5.10$, both the orders will remain in open state, unless one wish to change his price, this is an example of limit order. Market orders If seller is ready to sell 10 shares @ 5$ and another 10 shares @5.05$, if buyer wants to buy 20 shares @ market price, then the trade will be executed for 10 shares @ 5$ and another 10 shares @ 5.05$ The Limit Order are matched based on amount and time. The orders are listed Highest to Lowest on the Buy Side. The orders are listed Lowest to Highest on the Sell Side. If there are 2 Sell orders for same amount the order which is first in time [fractions of milliseconds] is first.  The about is the example as to how the orders would look like on any exchange.  Now the highest price the buyer is ready to pay is 20.21 and the lowest price a seller is ready to sell for is 20.25. Hence there is no trade. Now if a new Buy order comes in at 20.25, it matches with the sell and the deal is made. If a new Buy order comes in at 20.30, it still matches at 20.25. Similarly if a Sell order come in at 20.21, it matches and a deal is made. If a Sell order come in at 20.11, it still matches 20.21.   Incase of market order, with the above example if there is a Buy order, it would match with the lowest sell order at 20.25, if there is not enough quantity , it would match the remaining quantity to the next highest at 20.31 and continue down. Similarly if there is a Sell market order, the it would match to the maximum a seller is ready to buy, ie 20.21, if there is not sufficient buy quantity at 20.21, it will match with next for 20.19   If say there are new buy order at 20.22 and sell orders at 20.24, these will sit first the the above queue to be matched. In your above example the Lowest Sell order was at 20.10 at time t1 and hence any buy order after time t1 for amount 20.10 or greater would match to this and the price would be 20.10. However if the Buy order was first ie at t1 there was a buy order for 20.21 and then at time later than t1, there is a sell order for say 20.10 [amount less than or equal to 20.21] it would match for 20.21. Essentially the market looks at who was the first to sell at lower price or who was the first to buy at higher price and then decide the trade.  Edit [To Clarify xyz]: Say if there is an Sell order at $10 Qty 100. There is a buyer who is willing to pay Max $20 and is looking for Qty 500. Your key assumption that the Buyer does not know the current SELL price of $10 is incorrect. Now there are multiple things, the Buyer knows the lowest Sell order is at $10, he can put a matching Buy order at $10 Qty 100, and say $11 Qty 100 etc. This is painful. Second, lets say he puts a Buy order at $10 Qty 100, by the time the order hits the system someone else has put the trade at $10 and his order is fulfilled. So this buyer has to keep looking at booking and keep making adjustments, if its a large order, it would be extremely difficult and frustrating for this Buyer. Hence the logic of giving preference. The later Buy order says ... The Max I can pay is $20, match eveything at the current price and get the required shares. "Market orders do not get priority over limit orders.  Time is the only factor that matters in price/time order matching when the order price is the same. For example, suppose the current best available offer for AAPL is $100.01 and the best available bid is $100.00.  Now a limit buy for $100.01 and a market buy arrive at around the same instant.  The matching engine can only receive one order at a time, no matter how close together they arrive. Let's say that by chance the limit buy arrives first.  The engine will check if there's a matching sell at $100.01 and indeed there is and a trade occurs.  This all happens in an instant before the matching engine ever sees the market buy.  Then it moves on to the market buy and processes it accordingly. On the other hand, let's say that by chance the market buy arrives first.  The engine will match it with the best available sell (at $100.01) and a trade occurs.  This all happens in an instant before the matching engine ever sees the limit buy.  Then it moves on to the limit buy and processes it accordingly. So there's never a comparison between the two orders or their ""priorities"" because they never exist in the system at the same time.  The first one to arrive is processed first; the second one to arrive is processed second." Buy and sell orders always include the price at which you buy/sell. That's how the market prices for stocks are determines. So if you want to place a buy order at 106, you can do that. When that order was fulfilled and you have the stock, you can place a sell order at 107. It will be processed as soon as someone places a buy order at 107. Theoretically you can even place sell orders for stocks you haven't even bought yet. That's called short selling. You do that when you expect a stock to go down in the future. But this is a very risky operation, because when you mispredict the market you might end up owing more money than you invested. No responsible banker will even discuss this with you when you can not prove you know what you are doing. Many of the Bitcoin exchanges mimic stock exchanges, though they're much more rudimentary offering only simple buy/sell/cancel orders.  It's fairly normal for retail stock brokerage accounts to allow other sorts of more complex orders, where once a certain criteria is met, (the price falls below some $ threshold, or has a movement greater than some %) then your order is executed.  The space between the current buy order and the current sell order is the bid/ask spread, it's not really about timing.  Person X will buy at $100, person Y will sell at $102.  If both had a price set at $101, they would just transact.  Both parties think they can do a little bit better than the current offer.  The width of the bid/ask spread is not universal by any means.  The current highest buy order and the current lowest sell order, are both the current price.  The current quoted market price is generally the price of the last transaction, whether it's buy or sell. "There are two distinct questions that may be of interest to you. Both questions are relevant for funds that need to buy or sell large orders that you are talking about. The answer depends on your order type and the current market state such as the level 2 order book. Suppose there are no iceberg or hidden orders and the order book (image courtesy of this question) currently is:  An unlimited (""at market"") buy order for 12,000 shares gets filled immediately: it gets 1,100 shares at 180.03 (1,100@180.03), 9,700 at 180.04 and 1,200 at 180.05. After this order, the lowest ask price becomes 180.05 and the highest bid is obviously still 180.02 (because the previous order was a 'market order'). A limited buy order for 12,000 shares with a price limit of 180.04 gets the first two fills just like the market order: 1,100 shares at 180.03 and 9,700 at 180.04. However, the remainder of the order will establish a new bid price level for 1,200 shares at 180.04. It is possible to enter an unlimited buy order that exhausts the book. However, such a trade would often be considered a mis-trade and either (i) be cancelled by the broker, (ii) be cancelled or undone by the exchange, or (iii) hit the maximum price move a stock is allowed per day (""limit up""). Funds and banks often have to buy or sell large quantities, just like you have described. However they usually do not punch through order book levels as I described before. Instead they would spread out the order over time and buy a smaller quantity several times throughout the day. Simple algorithms attempt to get a price close to the time-weighted average price (TWAP) or volume-weighted average price (VWAP) and would buy a smaller amount every N minutes. Despite splitting the order into smaller pieces the price usually moves against the trader for many reasons. There are many models to estimate the market impact of an order before executing it and many brokers have their own model, for example Deutsche Bank. There is considerable research on ""market impact"" if you are interested. I understand the general principal that when significant buy orders   comes in relative to the sell orders price goes up and when a   significant sell order comes in relative to buy orders it goes down. I consider this statement wrong or at least misleading. First, stocks can jump in price without or with very little volume. Consider a company that releases a negative earnings surprise over night. On the next day the stock may open 20% lower without any orders having matched for any price in between. The price moved because the perception of the stocks value changed, not because of buy or sell pressure. Second, buy and sell pressure have an effect on the price because of the underlying reason, and not necessarily/only because of the mechanics of the market. Assume you were prepared to sell HyperNanoTech stock, but suddenly there's a lot of buzz and your colleagues are talking about buying it. Would you still sell it for the same price? I wouldn't. I would try to find out how much they are prepared to buy it for. In other words, buy pressure can be the consequence of successful marketing of the stock and the marketing buzz is what changes the price." "The risk of market orders depends heavily on the size of the market and the exchange. On big exchange and a security which is traded in hue numbers you're likely that there are enough participants to give you a ""fair"" price. Doing a market order on a security which is hardly dealed you might make a bad deal. In Germany Tradegate Exchange and the sister company the bank Tradegate AG are known to play a bit dirty: Their market is open longer than Frankfurt (Xetra) and has way lower liquidity. So it can happen that not all sell or buy orders can be processes on the Exchange and open orders are kept. Then Tradegate AG steps in with a new offer to full-fill these trades selling high or buying low. There is a German article going in details on wiwo.de either German or via Google Translate" Obvious answer but the limit order should be set at the price that you are willing to pay :). More usefully, if you want a decent chance of the order filling in short notice you should place the order one price tick above the current highest buyer (bid price). As long as high frequency trading remains alive I would advise against ever using market orders, these algorithmic trades can occasionally severely distort the price of a security in a fraction of a second. So if your market order happens to fill in during such a distortion you might end up massively overpaying/underselling.