How to calculate how far a stock price can drop before a broker would issue a margin call?
With your numbers, look at it this way - You borrowed $50. When the stock is $100, you are at 50% margin.  What's most important, is that there's margin interest charged, so the amount owed will increase regardless of the stock price. When calculating your return or loss, the interest has to be accounted for or your numbers will be wrong. For a small investor, margin rates can run high, and often, will offset much of your potential gain. What good is a $100 gain if you paid $125 in margin interest?
I'm not entirely sure about some of the details in your question, since I think you meant to use $10,000 as the value of the futures contract and $3 as the value of the underlying stock. Those numbers would make more sense. That being said, I can give you a simple example of how to calculate the profit and loss from a leveraged futures contract. For the sake of simplicity, I'll use a well-known futures contract: the E-mini S&P500 contract. Each E-mini is worth $50 times the value of the S&P 500 index and has a tick size of 0.25, so the minimum price change is 0.25 * $50 = $12.50.  Here's an example. Say the current value of the S&P500 is 1,600; the value of each contract is therefore $50 * 1,600 = $80,000. You purchase one contract on margin, with an initial margin requirement1 of 5%, or $4,000. If the S&P 500 index rises to 1,610, the value of your futures contract increases to $50 * 1,610 = $80,500. Once you return the 80,000 - 4,000 = $76,000 that you borrowed as leverage, your profit is 80,500 - 76,000 = $4,500.  Since you used $4,000 of your own funds as an initial margin, your profit, excluding commissions is 4,500 - 4,000 = $500, which is a 500/4000 = 12.5% return. If the index dropped to 1,580, the value of your futures contract decreases to $50 * 1,580 = $79,000. After you return the $76,000 in leverage, you're left with $3,000, or a net loss of (3,000 - 4000)/(4000) = -25%. The math illustrates why using leverage increases your risk, but also increases your potential for return. Consider the first scenario, in which the index increases to 1,610. If you had forgone using margin and spent $80,000 of your own funds, your profit would be (80,500 - 80,000) / 80000 = .625%. This is smaller than your leveraged profit by a factor of 20, the inverse of the margin requirement (.625% / .05 = 12.5%). In this case, the use of leverage dramatically increased your rate of return.  However, in the case of a decrease, you spent $80,000, but gained $79,000, for a loss of only 1.25%. This is 20 times smaller in magnitude than your negative return when using leverage. By forgoing leverage, you've decreased your opportunity for upside, but also decreased your downside risk. 1) For futures contracts, the margin requirements are set by the exchange, which is CME group, in the case of the E-mini. The 5% in my example is higher than the actual margin requirement, which is currently $3,850 USD per contract, but it keeps the numbers simple. Also note that CME group refers to the initial margin as the performance bond instead. "An attempt at a simple answer for the normal investor: A normal investor buys stock then later sells that stock. (This is known as ""going long"", as opposed to ""going short"").  For the normal investor, a stop order (of either kind) is only used when selling. A stop-loss sell order (or stop sell) is used to sell your stock when it has fallen too much in price, and you don't want to suffer more losses.  If the stock is at $50, you could enter a stop sell at $40, which means if the stock ever falls to $40 or lower, your stock will be sold at whatever price is available (e.g. $35). A stop-loss limit sell order (or stop limit sell) is the same, except you are also saying ""but don't sell for less than my limit price"".  So you can enter a stop limit sell at $40 with a limit of $39, meaning that if the stock falls to $40, you will then have a limit order in effect to sell the stock at $39 or higher.  Thus your stock will never be sold at $35 or any value below $39, but of course, if the stock falls fast from $40 to $35, your limit sell at $39 will not be done and you will be left still owning the stock (worth at that moment $35, say)." "The margin rules are also more complicated.  A simple buy on a non-margin account will never run into margin rules and you can just wait out any dips if you have confidence the stock will recover.  A ""simple"" short sell might get you a call from your broker that you have a margin call, and you can't wait it out without putting more money in.  Personally I have trouble keeping the short sale margin rules straight in my head, at least compared to a long sale. I got in way over my head shorting AMZN once, and lost a lot of money because I thought it was overvalued at the time, but it just kept going up and I wanted it to go down.   I've never gotten stuck like that on a long position." In the money puts and calls are subject to automatic execution at expiration. Each broker has its own rules and process for this.  For example, I am long a put. The strike is $100. The stock trades at the close, that final friday for $90. I am out to lunch that day. Figuratively, of course. I wake up Saturday and am short 100 shares. I can only be short in a margin account. And similarly, if I own calls, I either need the full value of the stock (i.e. 100*strike price) or a margin account.  I am going to repeat the key point. Each broker has its own process for auto execution. But, yes, you really don't want a deep in the money option to expire with no transaction.  On the flip side, you don't want to wake up Monday to find they were bought out by Apple for $150. A bullish (or 'long') call spread is actually two separate option trades.  The A/B notation is, respectively, the strike price of each trade. The first 'leg' of the strategy, corresponding to B, is the sale of a call option at a strike price of B (in this case $165).  The proceeds from this sale, after transaction costs, are generally used to offset the cost of the second 'leg'. The second 'leg' of the strategy, corresponding to A, is the purchase of a call option at a strike price of A (in this case $145). Now, the important part: the payoff.  You can visualize it as so. This is where it gets a teeny bit math-y.  Below, P is the profit of the strategy, K1 is the strike price of the long call, K2 is the strike price of the short call, T1 is the premium paid for the long call option at the time of purchase, T2 is the premium received for the short call at the time of sale, and S is the current price of the stock.  For simplicity's sake, we will assume that your position quantity is a single option contract and transaction costs are zero (which they are not). P = (T2 - max(0, S - K2)) + (max(0, S - K1) - T1) Concretely, let's plug in the strikes of the strategy Nathan proposes, and current prices (which I pulled from the screen).  You have: P = (1.85 - max(0, 142.50 - 165)) - (max(0, 142.50 - 145)) = -$7.80 If the stock goes to $150, the payoff is -$2.80, which isn't quite break even -- but it may have been at the time he was speaking on TV. If the stock goes to $165, the payoff is $12.20. Please do not neglect the cost of the trades!  Trading options can be pretty expensive depending on the broker.  Had I done this trade (quantity 1) at many popular brokers, I still would've been net negative PnL even if NFLX went to >= $165. To calculate any daily return, all one need do is divide the final value by the initial value, subtract 1, and multiply by 100%: This can be applied to either the futures alone, the investments used as margin collateral alone, or all together. Margin collateral as a factor of a derivative's return Collateral can take many forms. Many suggest that cost and revenue for a derivative trade should also take into account margin requirements.  This can become problematic. If a futures position moved against the trader, yet the margin was secured with equities at the maximum, and the equities moved with the trader, the futures trade could be interpreted as less of a loss because the collateral, which is probably totally disassociated with the futures position, increased in value. Then again, if a futures position moved with the trader, yet the margin collateral moved against the trader then taken together, the futures trade would look less profitable. Furthermore, most likely the result of a futures position and its collateral would never produce the same result, so extrapolation would become ever more difficult. For ease of analysis, a position's cost and revenue should be segmented from another unless if those positions are meant to hedge each other.  Margin is not a cost, but it is a liability, so margin will affect the balance sheet of a futures trade but not its income statement, again unless if the collateral is also used to hedge such futures position. They can sell a lower price call if they expect the stock to plummet in the near term but they are bullish on the longer term. What they are looking to do is collect the call premium and hope it expires worthless.  And then again 'hope' that the stock will ultimately turn around. So yes, a lot of hoping.  But can you explain what you mean by 'my brokerage gives premiums for prices lower than the current price'? Do you mean you pay less in commissions for ITM calls? It will depend largely on your broker what type of stop and trailing stop orders they provide. Saying that, I have not come across any brokers yet that offer limit orders with trailing stop orders.  Unlike a standard stop order where you can either make it a market stop order or a limit stop order, usually most brokers have trailing stop orders as market orders only, where you can either set the trailing stop to be a dollar value or percentage from the most recent high. Remember also, that trailing stop orders will be based on the intra-day highs and not the highest closing price. That means that if the share price spikes up during the day your trailing stop will move up, and if the price then spikes down you may be stopped out prematurely, after which the price might rally again. For this reason I try to base my trailing stops on the highest closing price by using standard stop loss orders and moving it up manually after the close of trade if the share price has closed at a new high. This takes a few minutes each evening (depending on how many stocks you have to check and adjust the stops for) but gives you more control. Using this method will also enable you to set limit orders attached to your stop loss triggers, and you won't have to keep your trailing too close to the last high price thus potentially causing you to get stopped out prematurely. Slightly off track but may be handy if you set profit targets, my broker has recently introduced Trailing Take Profit Orders. The way it works is, say you have a profit target of 50%, so you buy at $2 and want to take profits if the price reaches $3, you could set your Trailing Take Profit Trigger at say $3.10 or above and set a Trail by Amount of say $0.10. So if the price after hitting $3.10 falls to $3.00 you will be stopped out and collect your profits. If the price moves up to $3.30 and then falls to $3.20, you will be stopped out at $3.20 and make some extra profits. If the price continues going up the Trailing Take Profit will continue to move up always $0.10 below the highest price reached. I think this would be a very useful order if you were range trading where you could set the Trailing Take Profit trigger near recent resistance so you can get out if prices start reversing at or around the resistance, but continue profiting if the price breaks through the resistance. "You'd need to know the delta and the theta of the option. You can either calculate them yourself using a model like Black-Scholes (assuming you have a market price and can imply a volatility, and know the other factors that go into the model) or, you can see if your broker quotes ""greeks"" as well (mine does). The delta is the sensitivity (rate of change in value) to the underlying stock price, and the theta is the sensitivity to time passing (usually expressed in $/day).  So if your option has a delta of .5 and a theta of -.04, when one day passes and the underlying stock goes up $3, the option will gain roughly $1.50 due to the underlying stock price and lose $0.04 due to time passing." "Why would people sell below the current price, and not within the range of the bid/ask? There are many scenarios where this is deliberate but all of them boil down to the fact that the top level's bid doesn't support the quantity you're trying to sell (or is otherwise bogus[1]). One scenario as an example: You're day-trading both sides but at the end of the day you accumulated a rather substantial long position in a stock.  You don't want to (or aren't allowed to[2]) be exposed overnight, however.  What do you do? You place an order that is highly likely to go through altogether.  There's several ways to achieve that but a very simple one is to look at the minimum bid level for which the bid side is willing to take all of your shares, then place a limit order for the total quantity at that price.  If your position doesn't fit into the top level bid that price will well be lower than the ""current"" bid. Footnotes: [1] Keyword: quote stuffing [2] Keyword: overnight margin (aka positional margin, as opposed to intraday margin), this is highly broker dependent, exchanges don't usually distinguish between intraday and overnight margins, instead they use the collective term maintenance margin" "Probably the most significant difference is the Damocles Sword hanging over your head, the Margin Call. In a nutshell, the lender (your broker) is going to require you to have a certain amount of assets in your account relative to your outstanding loan balance. The minimum ratio of liquid funds in the account to the loan is regulated in the US at 50% for the initial margin and 25% for maintenance margins. So here's where it gets sticky. If this ratio gets on the wrong side of the limits, the broker will force you to either add more assets/cash to your account t or immediately liquidate some of your holdings to remedy the situation. Assuming you don't have any/enough cash to fix the problem it can effectively force you to sell while your investments are in the tank and lock in a big loss. In fact, most margin agreements give the brokerage the right to sell your investments without your express consent in these situations. In this situation you might not even have the chance to pick which stock they sell. Source: Investopedia article, ""The Dreaded Margin Call"" Here's an example from the article: Let's say you   purchase $20,000 worth of securities   by borrowing $10,000 from your   brokerage and paying $10,000 yourself.   If the market value of the securities   drops to $15,000, the equity in your   account falls to $5,000 ($15,000 -   $10,000 = $5,000). Assuming a   maintenance requirement of 25%, you   must have $3,750 in equity in your   account (25% of $15,000 = $3,750).   Thus, you're fine in this situation as   the $5,000 worth of equity in your   account is greater than the   maintenance margin of $3,750. But   let's assume the maintenance   requirement of your brokerage is 40%   instead of 25%. In this case, your   equity of $5,000 is less than the   maintenance margin of $6,000 (40% of   $15,000 = $6,000). As a result, the   brokerage may issue you a margin call. Read more: http://www.investopedia.com/university/margin/margin2.asp#ixzz1RUitwcYg" If you want to invest in the stock market, whether over a shorter period of 1 to 2 years or over a longer period of 10 or 20 years or longer you need to take some precautions and have a written investment plan with a risk management strategy incorporated in your plan. Others have said that 1 to 2 years is too short to invest in the stock market as the stock market can have a correction and fall by 50%. But it doesn't matter if you invest for 1 year or if you invest for 50 years, the stock market can still fall by 50% just before you plan to withdraw your funds. What you need to figure out is a way to get out before the market falls by 40% to 50%. A simple way to do this is to use technical indicators to warn you when a market trend is starting to change and that it is time to get out of the market. Two simple indicators you can use on a market index are the Rate of Change (ROC) indicator and the 100 week Moving Average (MA). Below is a 10 year weekly chart of the S&P500 with these two indicators charted. They show good times to get into the market and good times to get out.  If you are using the 100 week MA you would buy in when the price crosses above the MA line and sell when the price crosses below the MA line. If you are using the ROC indicator you would buy in when the ROC indicator crosses above the zero line and sell when the ROC indicator crosses below the zero line. So your investment plan could be to buy an Index ETF representing the S&P500 when the ROC moves above zero and sell when it crosses below zero. You can also place a trailing stop loss of 10% to protect you in case of a sudden fall over a couple of days. You can manage your investments in as little as 10 minutes per week by checking the chart once per week and adjusting your stop loss order.  If you want to progressively add to your investment each month you could check the charts and only add any new funds if both the ROC is above zero and sloping upwards. Another option for adding new funds could be if the price is above the MA and moving further away from the MA. All these rules should be incorporated into your investment plan so that you are not basing your decisions based on emotions. There are many other Technical Analysis Indicators you could also learn about to make better educated decisions about your stock market investments. However, what I have provided here is enough for anyone to test over different indexes and time frames and do their own paper trading on to gain some confidence before placing any real money on the table. Thanks to this youtube video I think I understood the required calculation. Based on following notation: then the formula to find x is: I found afterwards an example on IB site (click on the link 'How to Determine the Last Stock Price Before We Begin to Liquidate the Position') that corroborate the formula above. "You can't do this automatically; you want to understand whether the drop is from a short-term high. is likely to be a short-term low, or reflects an actual change in how folks expect the company to do in the future. Having said that, some people do favor a strategy which resembles this, betting on what are known as ""the dogs of the Dow"" in the assumption that they're well trusted but not as strongly sought and therefore perhaps not bid up as strongly. I have no opinion on it; I'm just mentioning it for comparison." "if it opens below my limit order  What exactly are you trying to achieve here? If your limit order is for 100 and the stock opens ""below"" your limit order, say 99, then it is obviously going to buy it automatically.  also place a stop loss on the same order  Most brokers allow limit + stop loss order at the same time on same order.  What I conclude from your question is that you're with a broker that is using obscure technology. Get a better broker or maybe, retry phrasing your question correctly."