A bigger position is not always a bigger risk.
Your position size tells you how much you hold. Your trade risk estimates what you could lose if a stop executes as modeled. Those are different questions—and confusing them can make an apparently small trade dangerous.
Updated 14 Nov 2026 · Original educational material · Hypothetical examples, not live market data
One trade, three different numbers.
Imagine a $10,000 account and a trade entered at $100 per unit. Buying 20 units creates a $2,000 notional position. That does not mean $2,000 is the intended risk. If you plan to exit at a $95 stop, the price difference is $5 per unit, so a full 20-unit stop exit would lose about $100 before costs.
If the stop were $90 instead, the same 20 units would expose roughly $200 to the modeled price move. To preserve a $100 budget at that wider distance, you would take only 10 units. Same planned loss, different notional. The stop is an exit instruction or level, not a guarantee of the fill price.
The basic sizing formula.
First decide the account risk amount you are modeling. A risk fraction of 1% on $10,000 means $100. Next divide it by the modeled loss per unit: the unfavorable entry-to-stop distance plus appropriate entry and exit costs. This simple formula applies to a linear instrument with a consistent quote currency.
| Input or result | Tighter stop | Wider stop |
|---|---|---|
| Account / risk budget | $10,000 / $100 | $10,000 / $100 |
| Entry | $100 | $100 |
| Stop | $95 | $90 |
| Loss per unit | $5 | $10 |
| Position quantity | 20 units | 10 units |
| Entry notional | $2,000 | $1,000 |
| Modeled stop loss | $100 | $100 |
What changes when fees are included?
Keep the $100 entry, $95 stop and $100 risk budget. Assume a 0.1% entry fee and 0.1% stop-exit fee, both charged on their respective fill values, with no slippage. The total modeled loss per unit becomes $5 + $0.10 + $0.095 = $5.195.
Rounding down to whole units keeps the estimated stop loss within the $100 budget. A real exchange may have different minimum increments, fee tiers and stop execution behavior. A stop order may fill at a worse price than the one entered.
Notional is not margin. Margin is not risk.
At 5× illustrative leverage, a $2,000 notional position might require around $400 in initial margin before fees. The stop-loss estimate would still be $100 if its modeled fill and position quantity are unchanged. Leverage changes how much collateral funds the exposure; it does not make the price movement smaller.
Actual liquidation depends on the contract, mark price, maintenance tiers, funding, cross/isolated mode and other positions. The simple formula here is not a liquidation calculator, and a stop cannot be relied on to execute before liquidation or a sharp gap.
Three mistakes worth avoiding.
Starting from leverage
Choosing 20× first can hide how much of the account a reasonable price move threatens. Start with an actual monetary loss budget and a defensible stop scenario.
Ignoring execution costs
Commission, spread and adverse stop slippage all eat into the planned budget. If the unit increment is large, round down rather than exceed the modeled loss limit.
Treating a stop as guaranteed
Sudden gaps, illiquidity and venue-specific order rules can produce a worse exit. Modeled risk is conditional, not a hard ceiling on losses.
Frequently asked questions.
Is 1% risk per trade always appropriate?
No. One percent is just a common illustration, not a universal recommendation. The appropriate loss budget depends on capital needs, strategy uncertainty, correlated positions and what you can afford to lose.
Does a smaller position always have less risk?
Only if the stop distance and other assumptions are comparable. Ten units with a very distant stop can expose more money than twenty units with a nearby modeled stop.
Can I use the same formula for COIN-M contracts?
Not directly. Inverse coin-margined contracts have a different payoff and settlement currency. Use the separate COIN-M Position Size Calculator and verify the contract face value.
What happens if the price gaps past my stop?
Losses may exceed the amount estimated by entry minus stop. The calculation assumes a specified exit fill and cannot guarantee execution in disorderly markets.