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Futures Position Size Calculator

Enter your dollar risk budget and stop distance to see the largest whole-contract position that keeps your loss within budget if the stop is hit — including round-trip cost and an optional slippage assumption. This never recommends risking your entire account or a fixed percentage of a funded-account balance, and no result here is a guarantee.

Your trade

The most you're willing to lose on this trade if the stop is hit. This is a number you choose — not derived from your account size or any remaining buffer.
Your broker or prop firm's total commission and fees for one round-trip contract (in and out). See the fee guide for current rates by broker/prop firm. Enter 0 to exclude costs from the estimate.
Optional. Extra ticks to assume your stop fills worse than the exact stop price — a real-world buffer for fast-moving or thin markets. Leave blank to assume a perfect fill.
Optional. How much room is left before you'd breach a prop-firm drawdown or daily-loss rule. This is shown as context only — the recommended size is never increased to use up this buffer, and this calculator never recommends risking the entire buffer on one trade.

Your result

0 contracts fit your budget

Even 1 contract's estimated risk at this stop ($505.00, including round-trip cost) exceeds your $500.00 budget. Widen your risk budget, use a tighter stop, or consider a smaller contract (e.g. a micro) if one exists for this market.

The formula

contracts = floor(risk budget ÷ ((stop in ticks + slippage ticks) × tick value + round-trip cost))

The result is always rounded down to a whole number of contracts — you can't buy a fraction of a contract, and rounding up would risk more than your stated budget. Tick value and tick size come from the same contract-specification table Fillbook's journal uses to calculate every logged futures trade's P&L.

Assumptions and limitations

This assumes your stop actually fills at (or within your slippage assumption of) the stated price — a gap or a fast market can slip well past that in practice. Round-trip cost is whatever you enter; check your specific broker or prop firm's current rates (see the fee guide) rather than assuming a default. This tool sizes to a risk budget you choose, never to a fixed percentage of a funded-account balance, and never labels any quantity "safe" or "guaranteed" — prop-firm rules (daily loss, drawdown, consistency) can still be breached by a position sized correctly against your stop alone, which is why a remaining buffer is shown as context, not folded into the sizing math automatically.

Size every trade like this automatically, against your real account

Fillbook can check a trade against your account's actual remaining drawdown and daily-loss buffer before you take it — not just a one-off calculation.

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Frequently asked questions

Only if you enter your remaining buffer — and even then, only as a warning if the recommended size would exceed it. This calculator sizes from your own stated risk budget for this one trade, not automatically from your account's total remaining room, since risking an entire remaining buffer on a single trade is rarely what a trader actually wants.

Rounding to the nearest contract could round up, which means risking more than the budget you entered if the stop is hit. Rounding down guarantees the actual dollar risk at your stop stays at or under your stated budget.

It means even one contract's risk at this stop distance and cost exceeds what you're willing to lose. Your options are a wider risk budget, a tighter stop, or a smaller contract — a micro version of the same market (MES instead of ES, for example) if one exists.

Commissions/fees are included only if you enter a round-trip cost, and slippage only if you enter an assumed number of ticks — both default to being excluded (cost at 0, slippage blank) if left blank, so an empty field means "not modeled," not "assumed zero risk."

See the underlying math explained in Futures Position Sizing — Fillbook.Check your P&L on a filled trade with Futures P&L Calculator — Fillbook.Built for futures and prop-firm accounts — Futures Trading Journal — Fillbook.Free trading calculators