Profit and Loss in Trading: How to Measure What You Actually Made (or Lost)

Every trade has a result. That result is either a gain or a loss, and it can be expressed in two ways: as a dollar amount, and as a percentage of the capital invested. Most traders know both numbers exist. Fewer understand how they relate to each other — and why that relationship matters more than either number in isolation.

The Basic P&L Calculation

For a long position in stocks or crypto, the profit and loss formula is straightforward:

If you bought 100 shares of a stock at $50 and sold at $55:

For a short position, the sign flips — you profit when the price falls:

For Forex, where position size is expressed in lots, the formula accounts for the standard lot size of 100,000 units:

Dollar P&L vs. Percentage Return: Why Both Matter

The dollar result tells you the absolute impact on your account. The percentage return tells you the quality of the trade relative to what you invested. They measure different things.

A $500 gain on a $5,000 position is a 10% return. A $500 gain on a $50,000 position is a 1% return. Same dollar amount, very different implications for how well the trade worked relative to the capital deployed.

The third row illustrates a correctly sized trade: 33 shares, 1% of a $10,000 account at risk, 2:1 ratio target hit. The dollar gain is modest but the percentage return is solid and the risk was controlled.

P&L in the Context of Risk Management

A P&L number in isolation is almost meaningless without knowing how much was risked to achieve it. A +$200 gain sounds good. But if it came from a trade where $2,000 was at risk, the return is 10% on the position — but if the stop had triggered, the loss would have been -$2,000, which on a $10,000 account is -20%. That's not a risk-managed trade.

The correct way to evaluate a P&L result is always relative to the planned risk. If you risked $100 (1% of your account) and made $200, your trade returned 2R — twice your risk unit. That's the professional benchmark: measuring results in R-multiples, not just dollars.

Tracking P&L Over Time

Individual trade P&L is a data point. A series of trade P&Ls is a pattern. Tracking results over time — by market, by setup type, by holding period — reveals what's actually working and what isn't. Without this data, trading decisions are based on recent memory, which is biased toward the last few trades and unreliable as a basis for strategy evaluation.

The Profit/Loss Calculator gives you the exact P&L for any closed trade — in dollars, as a percentage, and for Forex, in pips. Use it after every trade, not just the memorable ones.