Position Size Calculator
Lots to trade for your balance, risk and stop distance
FX rates updated 12:40 BST
A 25-pip stop at 0.53 lots risks £98.32, which is 0.98% of your balance.
0.53
standard lots
- Risk amount (1% of £10,000)£100.00
- Pip value at 1.00 lot£7.42
- Stop distance25 pips
Worked example: sizing a trade to a 1% risk
A £10,000 account risking 1% with a 25-pip stop on GBP/USD trades 0.53 lots (20 July 2026 rates). The 1% limit caps the loss at £100; one pip on 1.00 standard lot is worth £7.42 in a GBP account, so £100 divided by (25 pips x that pip value) gives 0.53 lots after rounding down to the nearest 0.01. At that size the position risks £98.32, just under the limit, and each pip is worth £3.93.
Choosing the stop distance
Stop distance and position size move in inverse proportion: double the stop and the size halves, because the pounds at risk are fixed by your risk percentage before either is chosen. A wide stop with a small position risks the same pounds as a tight stop with a large one, which is why the stop belongs at the level where your trade idea is wrong rather than at the level that produces a comfortable lot size.
Enter your balance and account currency, the percentage you are prepared to lose if the stop is hit, the stop distance in pips, and the pair. The calculator returns the size in standard lots and units, the pip value at that size, and the exact money at risk. Sizes round down to the 0.01-lot step brokers accept, so the risk figure never exceeds your limit. Our stop-loss guide covers placing the level itself.
The position sizing formula
Lots = (balance x risk % / 100) / (stop-loss pips x pip value of 1.00 lot). The pip value term converts the pair's quote currency into your account currency, which is why the same trade sizes differently in GBP and USD accounts. Our pip value calculator shows that conversion on its own.
Every input is observable before the trade: balance from your account, risk percentage from your plan, stop distance from your chart, pip value from current exchange rates. Nothing here predicts the market. It only fixes the cost of being wrong.
Why risk percentage beats fixed lots
A percentage rule compounds downwards, which is what keeps a losing run survivable: ten consecutive losses at 1% leave 90.4% of the account, while the same run at 5% takes 40.1% of it. Trading a fixed lot size instead lets your risk drift as the balance changes and as you switch pairs with different pip values, so the tenth loss is a larger share of a smaller account than the first was.
| Risk per trade | Account remaining | Drawdown |
|---|---|---|
| 0.5% | 95.1% | 4.9% |
| 1% | 90.4% | 9.6% |
| 2% | 81.7% | 18.3% |
| 5% | 59.9% | 40.1% |
The ladder is arithmetic on the risk rule, not a market forecast: it assumes every trade loses the full stop. Our drawdown guide covers what recovering from each of these actually requires, which is the harder half.
The percentage rule also makes results comparable across pairs. A 25-pip stop on GBP/USD and a 40-pip stop on GBP/JPY carry the same pound risk once the position is sized to the stop. New traders can start with the framework in our beginner forex broker guide.
Stop-loss distance and volatility
Stops placed inside a pair's normal hourly range get hit by noise rather than by being wrong. Volatile pairs and news sessions need wider stops, and the formula compensates with a smaller position. The common mistake runs the other way: keeping the size fixed and tightening the stop to force the numbers, which turns one planned loss into several unplanned ones.
Sizing also has to fit within your margin, and where it does not, margin is the binding constraint and the position shrinks to fit both. Our margin calculator owns that side of the sum, including the FCA caps that set it and the close-out level underneath.
FAQs
What percentage of my account should I risk per trade?
Does position size depend on leverage?
Why does the calculator round lots down?
What if the calculated size is less than 0.01 lots?
Related pages
About the author
Justin Grossbard is the co-founder and head of research at CompareForexBrokers. He has traded forex since 1998, leads UK broker research and has personally reviewed every FCA-regulated broker on this site. His work has appeared in Forbes, Kiplinger and Finance Magnates, and he holds a Bachelor of Commerce (Honours) and a Master of Marketing.