To size a futures position around a fixed loss budget, divide the budget by the loss per unit from entry to stop, including the estimated entry and stop execution fees. That gives a quantity; notional is quantity multiplied by entry price, and leverage then estimates the margin for that notional. This keeps stop distance and modeled fees inside one risk allowance instead of calculating a size from price movement alone.
What the position-size estimate includes
First set an account equity amount and a risk percentage. Their product is the target loss budget:
risk budget = equity × risk percent ÷ 100
For the calculator's linear quantity model, let E be entry price, S be stop price, and f be the per-side fee percentage entered. Its estimated loss per unit is:
per-unit loss = |E − S| + (E + S) × f ÷ 100
quantity = risk budget ÷ per-unit loss
notional = quantity × E
estimated margin = notional ÷ leverage
estimated max loss = quantity × per-unit loss
The fee term uses both entry and stop notionals. The calculator applies the same fee percentage to each side, so this is suitable when one estimated rate is a reasonable stand-in for both executions. If your entry and stop would have different rates, the single fee input cannot represent that difference exactly. The model assumes a linear contract and a fill at the entered stop price. Funding, slippage, spread, partial fills, taxes, and price gaps through a stop are not included.
Stop placement determines the side in this calculator: a stop below entry implies a long, while a stop above entry implies a short. The absolute price distance contributes to loss per unit either way. The risk percentage is a sizing constraint, not a forecast that the stop will execute at exactly that price or that losses can never exceed the selected amount.
Worked example: keep stop loss and fees in a $50 budget
Assume account equity of $5,000, risk per trade of 1%, a long entry at $50,000, a stop at $48,000, a fee estimate of 0.05% per side, and leverage of 5×. These are round illustrative inputs for demonstrating the formula, not a recommended risk level or market quote.
The risk budget is $5,000 × 1 ÷ 100 = $50. Price movement from entry to stop is $2,000 per BTC. The fee allowance per BTC is ($50,000 + $48,000) × 0.05 ÷ 100 = $49. So the modeled total loss per BTC is $2,000 + $49 = $2,049.
Quantity is then:
$50 ÷ $2,049 = 0.024402147… BTC
At $50,000 entry, estimated notional is 0.024402147… × $50,000 = $1,220.11. At 5× leverage, estimated margin is $1,220.11 ÷ 5 = $244.02. The modeled maximum loss at the stop, including its two fee allowances, is quantity × $2,049 = $50 before display rounding. Of that amount, about $48.80 comes from the price move and $1.20 from the modeled fees.
Enter those equity, risk, entry, stop, fee, and leverage assumptions in the position size calculator. Use the calculator to see the position size implied by the budget. The margin output is separate: it estimates how much margin the notional takes at the leverage entered. It is not an additional loss allowance and should not be substituted for the risk budget.
Why leverage and stop risk are different inputs
If quantity and stop remain fixed, changing leverage does not change the price movement or estimated fees at the stop. It changes the margin estimate because margin is notional divided by leverage. This is why sizing first from available leverage or desired margin can produce a position whose stop loss exceeds the amount you intended to risk.
For example, the position above has approximately $1,220.11 notional at 5×, so modeled margin is approximately $244.02. At 10×, with identical quantity and prices, the margin estimate would halve to about $122.01 while the stop loss calculation would remain about $50. In practice, exchange margin requirements and liquidation mechanics may differ from this simplified estimate. If you change leverage, maintain the same quantity when comparing stop risk; if you change quantity, recompute the risk.
If the calculated margin is greater than equity, the tool flags that condition. A lower estimate does not guarantee the order is permitted or safe: fees, maintenance margin, other positions, risk limits, and venue-specific rules may affect available balance. Use the leverage calculator to relate notional, margin, and leverage, and the crypto fee calculator to compare fee assumptions. Treat each tool as an estimate and reconcile the inputs with the venue where you trade.
A practical sizing sequence
- Choose the equity base you intend to use. Be consistent about whether this is total account equity or a smaller allocated amount.
- Set the maximum loss amount or risk percentage for the idea before choosing leverage.
- Enter the planned entry and stop prices. Confirm that the stop is on the loss side of entry for the intended direction.
- Enter the estimated per-side fee percentage. Use a conservative applicable estimate if the eventual order type is uncertain, then remember that the model uses the same rate on entry and exit.
- Read the quantity and notional. Check whether the quantity fits contract increments and any venue limits; the calculator does not round to venue lot steps.
- Review margin at the chosen leverage, but do not mistake lower margin for lower stop risk.
- Consider omitted costs and execution risk. If price can gap or slip past the stop, the realized loss can exceed this estimate.
This process turns risk into a position quantity. It does not decide whether a trade is worthwhile, where a stop belongs, or how likely the stop is to fill. Those are separate decisions that the calculator cannot infer from equity and prices alone.
Common mistakes
- Using only the entry-to-stop distance. The calculator also allocates for estimated fees on entry and stop exit. Ignoring fees understates the modeled loss per unit.
- Entering a fee as a decimal fraction. The field is in percent units: enter 0.05 for 0.05%, not 0.0005.
- Confusing margin with risk. Margin is collateral estimate; the stop-to-entry loss plus fees is the modeled risk amount.
- Assuming leverage reduces the loss on a fixed quantity. It reduces estimated margin for the same notional. A fixed quantity at the same stop has the same modeled dollar loss.
- Using an unsuitable equity base. If only part of an account is allocated to the strategy, using the entire balance changes the risk budget and resulting quantity.
- Assuming exact stop execution. Gaps, slippage, spread, and partial fills can make the loss larger than the entered stop-price estimate.
- Applying one fee to trades with different entry and exit costs. The calculator has one fee field. If rates differ, use a conservative approximation and account for the difference separately.
- Forgetting contract increments. The returned quantity may need rounding to a venue's permitted step. Recalculate the rounded quantity's loss before placing an order.
FAQ
Does this calculation include fees in the risk amount?
Yes. It adds the estimated fee at entry and at the stop exit to the price distance per unit, then sizes quantity so the combined modeled loss equals the risk budget.
Does using more leverage reduce my stop-loss dollar risk?
Not if quantity, entry, stop, and fee rate stay the same. Leverage changes the estimated margin needed for the notional position. A different quantity changes risk and requires a new calculation.
What if my entry and exit fees are different?
This tool applies one fee percentage to both sides. Use an approximation that reflects your expected trade, then calculate the two sides separately if the difference is material.
Are funding payments included?
No. Funding depends on the rate and settlements during the holding period. Estimate that separately with the funding fee calculator and consider it an additional cost outside this stop-loss estimate.
Can I lose more than the result shown as maximum loss?
Yes. The estimate assumes fills at the entered prices and excludes slippage, gaps, and other costs. A stop order does not guarantee an execution price.
Not financial advice. This is a position-sizing estimate, not a recommendation to trade.