See exactly how much a trade will cost you if it hits your stop — in dollars, in percent, and as a share of your account.
A stop loss is the price at which you agree, in advance, to admit a trade is wrong and get out. It is the single line between a normal losing trade and a catastrophic one. Yet most traders set stops by feel — a round number, a recent low, a level that "looks about right" — without ever translating that price into the one number that actually matters: how many dollars will I lose if this triggers? This calculator makes that number explicit before you risk a cent.
The math is straightforward. Your loss on a stopped-out trade is the number of shares you hold multiplied by the distance between your entry price and your stop loss price. A wider stop or a larger position both increase that loss in direct proportion. By entering your entry, your stop, and your share count, you instantly see the dollar loss, the loss per share, and — if you add your account balance — what fraction of your capital that single trade puts at risk.
That last figure is the one professionals watch. A trade that risks 5% of your account needs only a short string of losers to do serious damage, while a trade risking under 1% can be wrong many times in a row without threatening your survival. The point of a stop is not to be right; it is to keep every individual mistake small enough that your edge has room to play out over hundreds of trades. Seeing the real dollar and percentage cost before you enter is what keeps that discipline honest.
The calculator multiplies your share count by the price distance to your stop, then compares that dollar loss to your account balance.
Risk Per Share = |Entry Price − Stop Loss Price|
Total Dollar Loss = Risk Per Share × Number of Shares
% of Account at Risk = (Total Dollar Loss ÷ Account Balance) × 100
For example: entry at $150, stop at $147.50, 100 shares → $2.50 risk per share × 100 = $250 loss. On a $10,000 account that is 2.5% of capital at risk on one trade.
Your dollar loss equals the number of shares multiplied by the difference between your entry price and your stop loss price. Divide that by your account balance to see the loss as a percentage of your account.
There is no single correct percentage. Place the stop where the chart invalidates your trade idea, then size the position so that distance costs only 0.5–2% of your account. The stop distance should be driven by structure, not a fixed percentage.
Yes. On a short trade your stop loss sits above your entry price. The calculator uses the absolute difference between the two prices, so it works the same for longs and shorts.
The stop loss is the price where you exit a losing trade. Position size is how many shares you hold. Together they set your dollar risk. Use the Position Size Calculator to work backwards from a chosen risk to the correct share count.
A hard stop order placed with your broker executes automatically and removes emotion from the exit. Mental stops rely on discipline in the moment and are frequently ignored during fast moves. Most consistent traders use hard stops.
That is slippage. A standard stop becomes a market order once triggered, so in a fast or gapping market it fills at the next available price, which can be worse than your stop level. Volatile names and overnight gaps make this larger.
The most common mistake is placing the stop at a round dollar amount you are comfortable losing, rather than at a price the chart actually respects. When your stop sits just below an obvious support level or a recent swing low, it is far more likely to get hit by random noise. Give the level a little room, and let the resulting risk drive your size — not the other way around.
The second mistake is widening the stop after entry because the trade is moving against you. That converts a small planned loss into an unplanned large one and is how accounts quietly bleed out. Decide the stop before you enter and treat it as fixed. If you find your stops are always too tight, the fix is a smaller position, not a looser stop.
Pair this tool with the Position Size Calculator to turn a chart-based stop into the exact share count, the Risk/Reward Calculator to confirm the potential reward justifies the risk, and the Expectancy Calculator to check that your overall edge is positive across many trades.