Is it possible to improve stock purchase with limit orders accounting for volatility?
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. There is no such thing as buying at the best price. That only exists in hindsight. If you could consistently predict the lower bound, then you would have no reason to waste your time investing. Quit your job and bet with all leverage in. What if the price never reaches your lower bound and the market keeps rallying? What if today is crash day and you catch a falling knife? I'd say the best strategy would be just buy at whatever the market price is the moment your investment money hits your account with the smallest possible commission. The simplest solution to fire-and-forget is to pick something like a Target Date mutual fund made up of low-overhead index funds (within your 401k or a Roth IRA, perhaps) and set up automatic purchase to that.  If you're talking about limit orders and so on, that ain't simple.
I would say the most challenging fact for this assertion is that HFT firms operate with extremely limited capital bases. For a stock with say 10m shares ADV, even a very large and successful HFT strategy might use a position limit of no more than 5000 shares.  That is to say if you sum up and net the buys and sells for a stock across the day the HFT firm will never exceed 10,000 shares (2x position limits assuming it completely flipped) on a stock that trades 10,000,000 shares on a given day. The high volumes are attained through high turnover, the strategy might trade up to 500,000 shares (or 5% of the volume) attaining a 50x turnover.  But that brings me back to the original point. In the market microstructure literature market impact generally has been found to scale linearly or even sub-linearly for net volume executed.   If I alternate between thousands of 1 lot buy and sell orders, it would be very difficult for me to move the market because the market impact of every one of my buy orders roughly cancels the market impact of my almost exactly equal number of sell orders.   There might be a higher-order mechanism at work, but I'm genuinely curious what you think it might be. How could strategies that attain such small net positions have such out-sized impact on market direction? "In a way yes but I doubt you'd want that. A ""Stop-Limit"" order has both stop and limit components to it but I doubt this gives you what you want. In your example, if the stock falls to $1/share then the limit order of $3/share would be triggered but this isn't quite what I'd think you'd want to see. I'd suggest considering having 2 orders: A stop order to limit losses and a limit order to sell that are separate rather than fusing them together that likely isn't going to work." Market orders can be reasonably safe when dealing with stocks that are rather liquid and have quite low volatility. But it's important to note that you're trading a large degree of control over your buy / sell price for a small benefit in speed or complexity of entering an order. I always use limit orders as they help me guard against unexpected moves of the stock. Patience and attention to details are good qualities to have as an investor. Ok, so disregarding passivity, could you help me through a simplified example?   Say I only had two assets, SPY and TLT, with a respective weight of 35 and 65% and I want want to leverage this to 4x.  Additionally, say daily return covar is:  * B/B .004% * B/S -.004% * S/S .02%   Now, if I read correctly, I should buy ATM calls xxx days in the future.  Which may look like: Ticker, S, K, Option Price, Delta, Lambda  * TLT  $126.04  $126.00  $4.35  0.50  14.5 * SPY  $134.91  $134.00  $6.26  0.55  11.8  ^ This example is pretty close but some assets are far off.   I feel like I'm on the wrong track so I'll stop here.    I just want to lever up my risk-parity. Margin rates are too high and I'm docked by Reg-T. "Yes, almost always. I trade some of the most illiquid single stock options, and I would be absolutely murdered if I didn't try to work orders between the bid/ask.  When I say illiquid, I mean almost non-existent: ~50 monthly contracts on ALL contracts for a given underlying.  Spreads of 30% or more. The only time you shouldn't try to work an order, in my opinion, is when you think you need to trade immediately (rare), if implied volatility (IV) has moved to such a degree that the market makers (MM) won't hit your order while they're offering fair IV (they'll sometimes come down to meet you at their ""real"" price to get the exchange's liquidity rebate), or if the bid/ask spread is a penny. For illiquid single stock options, you need to be extremely mindful of implied and statistical volatility.  You can't just try to always put your order in the middle.  The MMs will play with the middle to get you to buy at higher IVs and sell at lower. The only way you can hope that an order working below the bid / above the ask will get filled is if a big player overwhelms the MMs' (who are lined up on the bid and ask) current orders and hits yours with one large order.  I've never seen this happen. The only other way is like you said: if the market moves against you, the orders in front of yours disappear, and someone hits your order, but I think that defeats the intent of your question." "You can certainly try to do this, but it's risky and very expensive. Consider a simplified example. You buy 1000 shares of ABC at $1.00 each, with the intention of selling them all when the price reaches $1.01. Rinse and repeat, right? You might think the example above will net you a tidy $10 profit. But you have to factor in trade commissions. Most brokerages are going to charge you per trade. Fidelity for example, want $4.95 per trade; that's for both the buying and the selling. So your 1000 shares actually cost you $1004.95, and then when you sell them for $1.01 each, they take their $4.95 fee again, leaving you with a measly $1.10 in profit. Meanwhile, your entire $1000 stake was at risk of never making ANY profit - you may have been unlucky enough to buy at the stock's peak price before a slow (or even fast) decline towards eventual bankruptcy.  The other problem with this is that you need a stock that is both stable and volatile at the same time. You need the volatility to ensure the price keeps swinging between your buy and sell thresholds, over and over again. You need stability to ensure it doesn't move well away from those thresholds altogether. If it doesn't have this weird stable-volatility thing, then you are shooting yourself in the foot by not holding the stock for longer: why sell for $1.01 if it goes up to $1.10 ten minutes later? Why buy for $1.00 when it keeps dropping to $0.95 ten minutes later? Your strategy means you are always taking the smallest possible profit, for the same amount of risk. Another method might be to only trade each stock once, and hope that you never pick a loser. Perhaps look for something that has been steadily climbing in price, buy, make your tiny profit, then move on to the next company. However you still have the risk of buying something at it's peak price and being in for an awfully long wait before you can cash out (if ever). And if all that wasn't enough to put you off, brokerages have special rules for ""frequent traders"" that just make it all the more complicated. Not worth the hassle IMO." 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. Have you looked into GnuCash? It lets you track your stock purchases, and grabs price updates. It's designed for double-entry accounting, but I think it could fit your use case. From your question, I am guessing that you are intending to have stoploss buy order. is the stoploss order is also a buy order ?  As you also said, you seems to limit your losses, I am again guessing that you have short position of the stock, to which you are intending to place a buy limit order and buy stoploss order (stoploss helps when when the price tanks). And also I sense that you intend to place buy limit order at the price below the market price. is that the situation?  If you place two independent orders (one limit buy and one stoploss buy). Please remember that there will be situation where two orders also get executed due to market movements. Add more details to the questions. it helps to understand the situation and others can provide a strategic solution. "I think that pattern is impossible, since the attempt to apply the second half would seem to prevent executing the first. Could you rewrite that as ""After the stock rises to $X, start watching for a drop of $Y from peak price; if/when that happens, sell."" Or does that not do what you want? (I'm not going to comment on whether the proposed programmed trading makes sense. Trying to manage things at this level of detail has always struck me as glorified guesswork.)" If one wants to have a bound on the loss percentages that are acceptable, this is would be a way to enforce that. For example, suppose someone wants to have a 5% stop-loss but doesn't want this to be worse than 10% as if the stock goes down more than 10% then the sell shouldn't happen. Thus, if the stock opened in a gap down 15% one day, this triggers the stop-loss and would exit at too low of a price as the gap was quite high as I wonder how familiar are you with how much a stock's price could change that makes the prices not be as continuous as one would think. At least this would be my thinking on a volatile stock where one may want to try to limit losses if the stock does fall within a specific range. This is to protect your position in specific highly volatile market conditions.  If the stock is free falling and you only have a stop order at $90, it's possible that this order could be filled at $50 or even less. The limit is to protect you from that, as there are certain very specific times where it's better to just hold the stock instead of taking a huge loss (ie when price is whipsawing). "Yes it is possible, as long as the broker you use allows conditional orders. I use CMC Markets in Australia, and they allow free conditional orders either when initially placing a buy order or after already buying a stock. See the Place New Order box below:  Once you have selected a stock to buy, the number of shares you want to buy and at what price you can place up to 3 conditional orders. The first condition is a ""Place order if..."" conditional order. Here you can place a condition that your buy order will only be placed onto the market if that condition is met first.  Say the stock last traded at $9.80 and you only want to place your order the next day if the stock price moves above the current resistance at $10.00. So you would Place order if Price is at or above $10.00. So if the next day the price moves up to $10 or above your order will be placed onto the market. The second condition is a ""Stop loss"" conditional order. Here you place the price you want to sell at if the price drops to or past your stop loss price. It will only be placed on to the market if your buy order gets traded. So if you wanted to place your stop loss at $9.00, you would type in 9.00 in the box after ""If at or below ?"" and select if you want a limit or market order. The third condition is a ""Take profit"" conditional order. This allows you to take profits if the stock reaches a certain price. Say you wanted to take profits at 50%, that is if the price reached $15.00. So you would type in 15.00 in the box after ""If at or above ?"" and again select if you want a limit or market order. These conditional orders can all be placed at the time you enter your buy order and can be edited or deleted at any time. The broker you use may have a different process for entering conditional orders, and some brokers may have many more conditional orders than these three, so investigate what is out there and if you are confused in how to use the orders with your broker, simply ask them for a demonstration in how to use them." If you find a particular stock to be overvalued at $200 for example and a reasonable value at $175, you can place a limit order at the price you want to pay. If/when the stock price falls to your desired purchase price, the transaction takes place. Your broker can explain how long a limit order can stay open. This method allows you to take advantage of flash crashes when some savvy stock trader decides to game the market. This tactic works better with more volatile or low-volume stocks. If it works for an S&P500 tracking ETF, you have bigger problems. :) Another tactic is to put money into your brokerage cash account on a regular basis and buy those expensive stocks & funds when you have accumulated enough money to do so. This money won't earn you any interest while it sits in the cash account, but it's there, ready to be deployed at a moment's notice when you have enough to purchase those expensive assets. Typically this isn't a random order- having a small volume just means it's not showing on the chart, but it is a vlid price point. Same thing would've happened if it would've been a very large order that shows on the chart. Consider also that this could have been the first one of many transactions that go far below your stop point - would you not have wanted it to be executed then, at this time, as it did? Would you expect the system to look into future and decide that this is a one time dip, and not sell; versus it is a crash, and sell? Either way, the system cannot look in the future, so it has no way to know if a crash is coming, or if it was a short dip; therefore the instrcutions are executed as given - sell if any transfer happens below the limit. To avoid that (or at least reduce the chance for it), you can either leave more distance (and risk a higher loss when it crashes), or trade higher volumes, so the short small dip won't execute your order; also, very liquid stocks will not show such small transaction dips.