Position sizing is the process of deciding how many contracts or how much notional value to put into a trade before you ever look at where you think price is going. Rather than starting with "how much do I want to make," a fixed-percentage approach starts with "how much am I willing to lose on this single trade if my stop is hit." That risk amount is then used, together with your stop distance, to calculate position size.
Why a fixed percentage of the account
One common educational framework is to define, before entering any trade, a maximum percentage of total account equity that a single trade is allowed to risk — for example, a hypothetical trader might choose 1% as a personal risk limit. This is not a rule that guarantees results; it is simply a way to keep any single losing trade from being disproportionately damaging to the account, and to make position size a mechanical calculation rather than a guess.
The percentage is applied to account equity, not to margin or to the notional size of the position. This distinction matters once leverage enters the picture, because leverage changes how much margin a position needs, but it does not by itself change how much you lose if your stop-loss is triggered — the loss in dollar terms is driven by price distance, not by leverage.
A worked hypothetical example
Assume a hypothetical account of 10,000 USDT. A trader decides, purely as an example, to risk 1% of equity per trade, which is 100 USDT.
Suppose the trader is considering a position and places a stop-loss 2% away from the planned entry price, based on chart structure. To find the position size that keeps the loss at 100 USDT if the stop is hit, the calculation is:
- Risk amount ÷ stop distance (%) = position size (notional)
- 100 USDT ÷ 2% = 5,000 USDT notional
In this hypothetical, a 5,000 USDT position with a stop 2% away loses approximately 100 USDT if the stop is filled — matching the 1% risk limit the trader set in advance. Note that this 5,000 USDT figure is the position's notional size, not the margin required to open it; margin depends separately on the leverage used.
How stop distance and leverage interact with size
Stop distance and position size move in opposite directions when risk is held constant. In the example above, if the trader instead placed the stop 4% away (a wider stop, perhaps to accommodate more volatility), the same 100 USDT risk budget would only support a 2,500 USDT notional position. A tighter stop of 1% away would allow a larger 10,000 USDT notional position for the same 100 USDT risk. The stop distance — not a preference for "more" or "less" leverage — is what primarily determines position size once the risk amount is fixed.
Leverage enters separately, as the tool that determines how much margin is set aside to support that notional position. Using the 5,000 USDT notional example: at 5x leverage, roughly 1,000 USDT of margin would be allocated; at 10x leverage, roughly 500 USDT of margin would be allocated for the same 5,000 USDT position. The dollar risk from the stop-loss stays at approximately 100 USDT in both cases, because it is driven by price distance and position size, not by leverage. What leverage changes is capital efficiency and how close the position sits to a liquidation price — a separate risk that a stop-loss is meant to prevent from being reached, but which can still occur if the stop is not filled as expected, for example during a fast move or an exchange outage.
Keeping the calculation consistent
A few points are easy to overlook when applying this kind of framework in practice:
- Recalculating equity periodically (rather than using the original deposit indefinitely) keeps the risk percentage aligned with the account's actual current size.
- Fees and funding payments on perpetual futures are separate from the stop-loss risk calculation but still affect overall results over time.
- A wider stop is not inherently "safer" than a tighter one — it simply changes the position size needed to keep dollar risk constant, and it also changes how much room price has to move before the stop is reached.
Leveraged crypto futures trading carries a high risk of loss, and no position-sizing method removes that risk or guarantees a particular outcome.
Keeping risk-per-trade consistent is easier when past trades are easy to review. BitMe's crypto trading journal automatically logs closed USDT/USDC futures trades from Bybit, OKX and BloFin, so traders can check position sizing and outcomes against their own plan over time.