Position Size Calculator
Work out how much to trade from the risk you are prepared to take: your account balance, the percentage you will risk, and how far away your stop sits.
Common questions
How do you calculate position size in forex?
Divide the cash you are willing to lose by the size of your stop in pips multiplied by the pip value of one lot. On a $10,000 account risking 1% ($100) with a 30-pip stop on EUR/USD, where one standard lot is worth $10 per pip, that is 100 / (30 x 10) = 0.33 standard lots. The account balance never enters the formula directly — only the cash amount it implies.
What percentage should I risk per trade?
Most retail risk-management guidance lands between 0.5% and 2% per trade. The honest answer is that the right number depends on your strategy's win rate and payoff, not on a rule of thumb — which is what the risk of ruin calculator is for. A strategy with a genuine edge still blows up if the position size is large enough for a normal losing streak to be fatal.
Should the spread be included in my stop loss distance?
Yes. Your stop is hit on the bid for a long and the ask for a short, so a 30-pip stop with a 1-pip spread is really 31 pips of cost. Ignoring it understates risk by a few percent on wide stops and by a lot on tight ones. Every backtest published on this site prices the spread from real per-minute tick data for exactly this reason.
Why does my broker's calculator give a different lot size?
Usually one of three things: a different pip value for the quote currency, a different account currency, or rounding to the broker's minimum lot step. Differences beyond a few percent normally mean the pip value is being computed at a stale exchange rate.
Is position size the same as lot size?
They are two halves of one decision. This page answers the risk question — how much should I trade given what I am prepared to lose. Lot size is the unit your broker accepts that quantity in, and what it commits you to differs sharply between FX and metals. The lot size calculator covers that side.
Where we use this
Every backtest we publish risks exactly 1% per trade using this same math.
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