How to use the stop-loss calculator
Enter the price you bought at (entry), the price where you'll cut the trade (stop-loss), and how many shares or coins you hold (quantity). The calculator shows the dollar loss if the stop is hit and that loss as a percentage of your entry. Add a take-profit target and it also shows your potential profit and your risk-reward ratio — the single most useful number for judging whether a trade is worth taking.
The formulas
Loss = |Entry − Stop| × Quantity · Loss % = |Entry − Stop| ÷ Entry × 100 · Risk : reward = |Target − Entry| ÷ |Entry − Stop|
Worked example
Buy 50 shares at $100, stop-loss at $90, target $120:
- Risk per share: $100 − $90 = $10
- Loss if stopped out: $10 × 50 = $500 (a 10% loss)
- Reward per share to target: $120 − $100 = $20 → profit $1,000
- Risk : reward = $20 ÷ $10 = 1 : 2 — you aim to make twice what you risk
How big should your stop-loss be?
There's no universal number. A tight stop risks getting shaken out by normal noise; a wide stop means a bigger loss if you're wrong. Many stock traders use a 5–15% stop, while volatile crypto often needs more room. The best place for a stop is where your trade idea is clearly wrong — not a round number chosen to justify a bigger position. Pair this tool with the Position Size Calculator to size the trade to a fixed risk first, then confirm the dollar loss here.
Why risk-reward matters more than win rate
You don't need to be right most of the time to make money — you need your winners to outweigh your losers. At a 1:2 risk-reward you can be wrong more than half the time and still come out ahead. Checking the ratio before you enter stops you taking trades where the downside dwarfs the upside.
Common mistakes to avoid
Moving your stop further away after entry to avoid being stopped out — that quietly turns a small planned loss into a big one. Ignoring fees and slippage, which make the real loss slightly larger than the price distance. Setting a target you don't actually believe in just to make the risk-reward look good. Risking more than a small, fixed share of your account on any one trade.
Frequently asked questions
50 shares at $100, stop $90 — how much do I lose?
$10 per share × 50 = $500, a 10% loss. Add a $120 target and your risk-reward is 1:2.
How do I calculate loss percentage?
Loss % = (Entry − Stop) ÷ Entry × 100. A $100 entry with a $90 stop is a 10% loss.
What is a good risk-reward ratio?
Many traders want at least 1:2 — risking $1 to make $2 — but it depends on your win rate and strategy.
What percentage should a stop-loss be?
It depends on volatility and strategy; 5–15% is common for stocks, wider for crypto. Place it where your idea is wrong.
Does it work for stocks and crypto?
Yes — use the entry and stop prices for any instrument and the quantity you hold.
Is my data saved?
No. Everything runs in your browser; nothing is uploaded.