Position Size Calculator
Calculate the ideal trade size based on your account balance, risk tolerance, and stop-loss level.
Enter your balance, entry, and stop-loss to size your trade safely.
Position sizing is the one thing separating traders who survive from traders who do not. It is not glamorous and nobody posts about it, but it is the entire game. This calculator answers the only question that matters before you enter: given what I am willing to lose, how big can this trade actually be?
The logic, backwards
Most people size positions by feel — 'I'll put in a thousand' — and then place a stop wherever the chart looks right. That is backwards, and it is why accounts die. The correct order is: decide what you will risk, decide where your idea is proven wrong, and let those two numbers dictate the size. You never choose the size directly. It falls out of the math. Say you have $10,000 and risk 1% — $100. Your entry is $60,000 and your stop is $58,000, a $2,000 distance. Then your position is $100 ÷ $2,000 = 0.05 BTC. Not because 0.05 felt right, but because that is the only size where being wrong costs exactly what you decided it would. The 1% rule exists for a reason. At 1% risk, ten consecutive losses cost you 10% of your account. At 10% risk, ten losses cost you 65%. Losing streaks are not hypothetical — every trader has them.
The formula
Risk Amount = Balance × Risk%
Stop Distance = |Entry − Stop|
Position Size = Risk Amount ÷ Stop Distance
Position Value = Position Size × Entry
Margin Needed = Position Value ÷ Leverage
Example: $10,000 balance, 1% risk, entry $60,000, stop $58,000
Risk = $100, Distance = $2,000
Size = 0.05 BTC → Value $3,000 → Margin at 10× = $300Notice that leverage does not appear until the last line. Leverage determines the margin you must post, not your risk. Your risk was fixed the moment you set the stop.
Sizing rules worth keeping
- 11–2% per trade is the standard for a reason. It means a losing streak is survivable and recoverable. Above 5%, a normal run of bad luck becomes an account-ending event.
- 2A wider stop means a smaller position, always. Beginners widen the stop to 'give the trade room' while keeping the same size — which silently doubles or triples their risk.
- 3Leverage is not risk. A 0.05 BTC position risks the same whether you use 1× or 20× — what changes is the margin posted and how close liquidation sits. Never let available leverage decide your size.
- 4Check that your liquidation price is far beyond your stop. If liquidation would trigger first, your stop is decorative and your real risk is the entire margin.
- 5Recalculate after every material change in balance. Risking 1% of your starting balance rather than your current one means you take too much risk after losses and too little after wins — exactly backwards.
Frequently asked questions
What percentage should I risk per trade?
1% is the widely accepted standard, 2% if you are experienced and confident. The math is unforgiving: at 1%, twenty straight losses leave you down 18% and still trading. At 10%, twenty straight losses leave you with 12% of your account and no realistic path back.
Does this work for spot trading too?
Yes. Set leverage to 1× and the margin required equals the full position value. The risk logic is identical — the only difference is that spot has no liquidation, so your stop is your only exit.
What if the calculated position is tiny?
Then that is the correct position, and the alternative is not 'trade bigger' — it is either take a tighter stop, or skip the trade. A small position on a good setup beats a large position that liquidates.
Should I include fees in the risk?
Ideally yes, though they are usually small relative to the stop distance. If you are trading with very tight stops — a few tenths of a percent — then fees become a meaningful part of your risk and should be modelled.
Why does required margin exceed my balance sometimes?
Because your stop is very tight, producing a large position. The math is right; the trade is not viable at that leverage. Either raise leverage — which moves liquidation closer, dangerous — or accept that this setup does not fit your account size.