How to calculate how far a shorted stock's price can rise before broker issues a margin call?
Most brokers have a margin maintenance requirement of 30%.  In your example, it would depend on how much money you're borrowing from your broker on margin. Consider this: You have $250, and short AAPL at $500 on margin. This would be a common scenario (federal law requires investors to have at least 50% of their margin equity when opening a transaction). If your broker had a requirement of 30%, they would require that for your $500 position, you have at least $500 * .3 = $150 equity. Since you are currently above that number at $250, you will not be hit with a margin call. Say the price of AAPL doubles, and now your position is worth $1000. $1000 * .3 = $300, which is $50 above your initial equity. Your broker will now consider you eligible for a margin call. Most will not execute the call right away, you will often have some time to either sell/cover stock or add funds to your account. But not all brokers will warn you if you are breaking margin requirements, and sometimes margin calls can take you by surprise if you are not paying attention. Also, many will charge interest on extra margin borrowed. "When margin is calculated as the equity percentage of an account, the point at which a broker will forcibly liquidate is typically called ""maintenance margin"". In the US, this is 25% for equities. To calculate the price at which this will occur, the initial and maintenance margin must be known.  The formula for a long with margin is: and for a short where P_m is the maintenance margin price, P_i is the initial margin price, m_i is the initial margin rate, and m_m is the maintenance margin rate.  At an initial margin of 50% and a maintenance margin of 25%, a long equity may fall by 1/3 before forced liquidation, a short one may rise by 50%. This calculation can become very complex with different asset classes with differing maintenance margins because the margin debt is applied to all securities collectively."
"There are three ways to do this. So far the answers posted have only mentioned two.  The three ways are: Selling short means that you borrow stock from your broker and sell it with the intent of buying it back later to repay the loan.  As others have noted, this has unlimited potential losses and limited potential gains.  Your profit or loss will go $1:$1 with the movement of the price of the stock. Buying a put option gives you the right to sell the stock at a later date on a price that you choose now.  You pay a premium to have this right, and if the stock moves against you, you won't exercise your option and will lose the premium.  Options move non-linearly with the price of the stock, especially when the expiration is far in the future.  They probably are not for a beginner, although they can be powerful if used properly. The third option is a synthetic short position.  You form this by simultaneously buying a put option and selling short a call option, both at the same strike price.  This has a risk profile that is very much like the selling the stock short, but you can accomplish it entirely with stock options.  Because you're both buying an selling, in theory you might even collect a small net premium when you open. You might ask why you'd do this given that you could just sell the stock short, which certainly seems simpler.  One reason is that it is not always possible to sell the stock short.  Recall that you have to borrow shares from your broker to sell short.  When many people want to short the stock, brokers will run out of shares to loan.  The stock is then said to be ""hard to borrow,"" which effectively prevents further short selling of the stock.  In this case the synthetic short is still potentially possible." A bit of poking around brought me to this thread on the Motley Fool, asking the same basic question: I think the problem is the stock price. For a stock to be sold short, it has to be marginable which means it has to trade over $ 5.00. The broker, therefore, can't borrow the stock for you to sell short because it isn't held in their clients' margin accounts. My guess is that Etrade, along with other brokers, simply exclude these stocks for short selling. Ivestopedia has an explanation of non-marginable securities. Specific to stocks under $5: Other securities, such as stocks with share prices under $5 or with extremely high betas, may be excluded at the discretion of the broker itself. "So, the term ""ready market"" simply means that a market exists in which there are legitimate buy/sell offers, meaning there are investors willing to own or trade in the security. A ""spot market"" means that the security/commodity is being delivered immediately, rather at some predetermined date in the future (hence the term ""futures market"").  So if you buy oil on the spot market, you'd better be prepared to take immediate delivery, where as when you buy a futures contract, the transaction doesn't happen until some later date.  The advantage for futures contract sellers is the ability to lock in the price of what they're selling as a hedge against the possibility of a price drop between now and when they can/will deliver the commodity.  In other words, a farmer can pre-sell his grain at a set price for some future delivery date so he can know what he's going to get regardless of the price of grain at the time he delivers it.  The downside to the farmer is that if grain prices rise higher than what he sold them for as futures contracts then he loses that additional money.  That's the advantage to the buyer, who expects the price to rise so he can resell what he bought from the farmer at a profit. When you trade on margin, you're basically borrowing the money to make a trade, whether you're trading long (buying) or short (selling) on a security.  It isn't uncommon for traders to pledge securities they already own as collateral for a margin account, and if they are unable to cover a margin call then those securities can be liquidated or confiscated to satisfy the debt.  There still may even be a balance due after such a liquidation if the pledged securities don't cover the margin call. Most of the time you pay a fee (or interest rate) on whatever you borrow on margin, just like taking out a bank loan, so if you're going to trade on margin, you have to include those costs in your calculations as to what you need to earn from your investment to make a profit. When I short trade, I'm selling something I don't own in the expectation I can buy it back later at a lower price and keep the difference.  For instance, if I think Apple shares are going to take a steep drop at some point soon, I can short them.  So imagine I short-sell 1000 shares of AAPL at the current price of $112.  That means my brokerage account is credited with the proceeds of the sale ($112,000), and I now owe my broker 1000 shares of AAPL stock.  If the stock drops to $100 and I ""cover my short"" (buy the shares back to repay the 1000 I borrowed) then I pay $100,000 for them and give them to my broker.  I keep the difference ($12,000) between what I sold them for and what I paid to buy them back, minus any brokerage fees and fees the broker may charge me for short-selling. In conclusion, a margin trade is using someone else's money to make a trade, whether it's to buy more or to sell short.  A short trade is selling shares I don't even own because I think I can make money in the process. I hope this helps." ISOs (incentive stock options) can be closed out in a cashless transaction. Say the first round vests, 25,000 shares. The stock is worth $7 but your option is to buy at $5 as you say. The broker executes and sells, you get $50,000, with no up front money.  Edit based on comment below - you know they vest over 4 years, but how long before they expire? It stands to reason the longer you are able to hold them, the better a chance the company succeeds, and the price rises.  The article Understanding employer-granted stock options (PDF) offers a nice discussion of different scenarios supporting my answer. 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. In my IRA I try to find stocks that are in growing sectors but have are undervalued by traditional metrics like PE or book value; I make sure that they have lower debt levels than their peers, are profitable, and at least have comparable margins.   I started trading options to make better returns off of indices or etfs. It seems overlooked but it's pretty good, in another thread I was telling someone about my strategy buy applying it to thier portfolio: https://www.reddit.com/r/options/comments/77bt17/ive_been_trading_stocks_for_a_year_and_am/dolydu8/?context=3  I double checked, I told him/her I would buy the DIA Jan 19 2018 call 225 for 795. 8 days later it's trading for 1085. Nearly 50% in a week. It'll never be 300% earnings returns, but I'm happy to take it slow.   Shorting is a very different animal it takes a lot to get things right. 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. It this a real situation or is it a made up example? Because for a stock that has a last traded priced of $5 or $6 and volume traded over $4M (i.e. it seems to be quite liquid), it is hardly likely that the difference from bid to ask would be as large as $1 (maybe for a stock that has volume of 4 to 5 thousand, but not for one having volume of 4 to 5 million). In regards to your question, if you were short selling the order would go in exactly the same as if you were selling a stock you owned. So your order would be on the ask side and would need to be matched up with a price on the bid side for there to be a trade.