Position size calculator
Enter your balance, risk per trade, entry and stop. The calculator works backwards to the largest position that keeps a stop-out inside your risk, fees included.
A stop-out costs $9.99, within your 1.00% rule, and liquidation is beyond your stop.
How the position size is calculated
The idea is simple: decide how much you’re willing to lose, then divide by how much you lose per coin if the stop is hit.
Risk budget = balance × risk %
Cost per coin = |entry − stop| + (entry + stop) × fee per side
Size = risk budget ÷ cost per coin, rounded down to the size step
The fee part matters on perpetual futures: you pay a fee to open and another to close, on the full position value. Leaving it out means every losing trade costs a little more than you planned.
What leverage changes (and what it doesn’t)
Leverage doesn’t change the size or the loss at your stop. It only changes the margin the exchange locks up and how close the liquidation price is. The calculator warns you when the margin is more than your balance or when liquidation would come before your stop.
About the numbers
- Loss if stopped is the price loss plus opening and closing fees. Funding isn’t included, as it depends on how long you hold.
- Liquidation is a rough estimate for isolated margin with a 0.5% maintenance margin. Your exchange’s own figure may differ.
- Size step is the smallest amount your exchange lets you trade (for example 0.001 BTC). The size is always rounded down.