Profit/Loss Calculator
The dollar figure is only half the picture — the percentage return and the fees decide whether a trade was actually worth the risk. This works for both a long (you profit when price rises) and a short (you profit when it falls), and nets out fees on both sides.
- • Long P&L = (exit − entry) × size. Short P&L = (entry − exit) × size.
- • Net P&L = gross − total fees. Return = net ÷ (entry × size).
Worked example: buy 100 shares at $100 and sell at $115 — gross profit $1,500, a +15% return before fees.
Return is shown on the position's cost. Ignores taxes, slippage, and (for shorts) borrow costs — all real. Educational tool, not advice.
A free, interactive calculator for any blog, newsletter or forum — same numbers as here, and it links back.
<iframe src="https://stratsemble.com/embed/tools/profit-loss-calculator" width="460" height="450" style="border:0;border-radius:12px;max-width:100%" loading="lazy" title="Profit / loss calculator — Stratsemble"></iframe>A calculator shows what a rule should do on paper. A backtest is how you find the rare few that actually beat simply buying and holding — costs on, losses shown, no look-ahead — so when you build one that survives, you'll know it isn't a fake edge, and can prove it forward before you risk real money. It won't tell you you'll win — nothing honest can.