How the position size is calculated
Size = Risk ÷ (|Entry − Stop| + Entry × opening fee + Stop × closing fee)
The result is rounded down to the contract's quantity step on Bitget, so the loss at your stop never exceeds what you set. Fees are part of the formula because a tight stop on a small price move can cost noticeably more than planned once both fees are counted. A stop-market order fills as a taker, so the closing fee defaults to the taker rate.
Worked example
A 1,000 USDT account risking 1% (10 USDT) on a long ETH trade, entry 2,500, stop 2,450, 0.05% fees on both sides.
Loss per ETH = 50 + 1.25 + 1.225 = 52.475 USDT. Size = 10 ÷ 52.475 = 0.1905, rounded down to 0.190 ETH, a 475 USDT position. At 10x it needs 47.50 USDT of margin.
Sizing on Bitget
Bitget quotes these contracts in USDT. The calculator reads each contract's order step and minimum size from Bitget's API. The fee fields start at Bitget's standard rates of 0.02% maker and 0.06% taker. The liquidation check uses Bitget's liquidation formula.
Leverage doesn't change your risk, but it can skip your stop
Once the size is fixed, leverage only decides how much margin the position locks up. The loss at your stop stays the same. Push leverage too high, though, and the liquidation price moves in front of the stop: the position is liquidated before the stop can fire, and you lose the whole margin plus the liquidation fee. The calculator shows the highest leverage that still keeps the stop first.
Frequently asked questions
How much of my account should I risk per trade?
Many traders keep it between 0.5% and 2% so that a losing streak doesn't wipe out the account. The right number depends on your strategy and how often it loses in a row. This calculator does the arithmetic; it does not make the choice for you.
Why is my size rounded down?
Exchanges only accept quantities in steps set for each contract, such as 0.001 BTC. Rounding down keeps the loss at your stop at or below your risk amount.
Should I use the maker or taker fee for the stop?
Stop-market orders fill as taker orders. If you close with a limit order that rests on the book, the maker fee applies instead.
Does slippage matter?
Yes. In a fast market a stop-market order can fill past your stop price, so the real loss can be larger than calculated. Leave some room in your risk amount for volatile contracts.