Direct answer：Position size should be derived from the maximum loss you choose for the trade, not from leverage first. This tool uses account equity, risk percentage, entry, and stop price to calculate quantity. It is a risk-budget model, not a trade recommendation, and it cannot guarantee a stop fill at the selected price.
Set the loss budget before solving for size
Per-trade risk equals strategy account equity multiplied by a chosen risk fraction. A wider entry-to-stop distance creates more potential loss per unit, so the same loss budget supports fewer units.
The risk fraction is the user's constraint, not a universal standard. The 1% figure in the example is only a reproducible teaching input, not a recommendation.
- A long stop is generally below entry; a short stop is generally above entry.
- Account equity should include only capital actually allocated to the trading strategy.
- Without a defined stop or invalidation point, this model cannot define per-unit risk.
Position quantity formula
Let A be account equity, p the per-trade risk fraction, E entry price, and S stop price. When costs are included, f is the estimated round-trip fee rate and s the estimated slippage rate.
Fees and slippage are approximated as a share of entry notional to reserve room in the loss budget; this is not an execution guarantee.
Risk budget = A × pRisk per unit = |E − S| + E × (f + s)Quantity = risk budget ÷ risk per unitNotional = quantity × EPosition size and leverage answer different questions
Position size determines the theoretical loss if price reaches the stop. Leverage primarily changes required initial margin and liquidation distance. More leverage does not automatically justify a larger loss budget for the same stop.
The calculated notional must still pass available-margin, maximum-leverage, minimum-order, and liquidation-distance checks. If estimated liquidation is closer than the stop, the leverage and margin setup is not directly executable as planned.
| Variable | Direct effect | Still verify |
|---|---|---|
| Higher risk fraction | Higher budget and quantity | Tolerance for a losing streak |
| Wider stop | Lower quantity for the same budget | A strategy-based stop level |
| Higher leverage | Lower initial margin | Liquidation does not precede the stop |
| Higher costs | Higher unit risk and lower quantity | Liquidity and order type |
The model cannot remove execution risk
A normal stop triggers an order; it does not guarantee a fill price. Fast markets, gaps, poor liquidity, partial fills, and the actual fee tier can make the realized loss larger than budgeted.
Round the output down to the venue's quantity step, then recalculate actual notional, estimated costs, and liquidation distance. Correlated positions can also make portfolio risk much larger even when each trade individually meets its budget.
- Do not count long-term holdings again as active strategy risk capital.
- Round quantity down rather than up so rounding does not exceed the budget.
- Use a more conservative slippage allowance in volatile or thin markets.
Worked example: Reproducible example: sizing a long with a 1% budget
- Strategy account equity A: 10,000 USDT
- Teaching risk fraction p: 1%, creating a 100 USDT risk budget
- Entry E: 50 USDT; stop S: 48 USDT
- Estimated round-trip fee f: 0.10%; estimated slippage s: 0.10%
- Price risk = |50−48| = 2 USDT per unit
- Cost allowance = 50×(0.001+0.001) = 0.10 USDT per unit
- Quantity = 100÷2.10 = 47.6190 units
- Notional = 47.6190×50 = 2,380.95 USDT
Before applying the venue quantity step, the model returns about 47.6190 units and 2,380.95 USDT notional.
Frequently asked questions
Is 1% a recommended risk percentage?
No. It is a common teaching example. Appropriate risk depends on capital purpose, strategy, volatility, tolerance for consecutive losses, and personal circumstances.
Is risk percentage the same as position size as a share of the account?
No. Risk percentage is the planned loss at the stop as a share of the account. Position notional can be larger or smaller than that amount.
Can higher leverage let me open a larger position?
It may reduce required initial margin, but it should not change the pre-set loss budget and it shortens liquidation distance. Size from risk first, then check leverage feasibility.
Why include fees and slippage in per-unit risk?
Using only the entry-to-stop move understates total loss. Fees reduce equity directly, while slippage can make the exit price worse than planned.
Can I use the formula without a stop-loss?
The formula needs a defined invalidation point to measure per-unit risk. Without an exit rule, the stated risk cap does not hold.
Official sources and checks
- Proper Position Size · CME GroupRecorded: 2026-08-31
Sizing from acceptable account loss and stop distance
- How to Calculate Position Size in Trading · Binance AcademyRecorded: 2026-08-31
Account risk, invalidation distance, formula, fees, and slippage limits
- A Beginner's Guide to Risk Management · Binance AcademyRecorded: 2026-08-31
Distinguishing risk amount from notional position size
How this page was produced: AI-assisted draft · automated release checks · 2026-08-31