In a personal account, risk per trade is a preference. Under an evaluation it's an output — determined entirely by the drawdown allowance and the length of losing streak you need to survive.
Get this number right and passing becomes a waiting game. Get it wrong and no amount of setup quality saves the account.
Start from the streak, not the comfort level
A strategy that wins 50% of the time will, over 100 trades, very often produce a run of 6 or 7 consecutive losses. Over 200 trades, 8 or 9 is unremarkable. These aren't disasters — they're the normal shape of randomness.
So the question isn't "what risk feels safe?" It's: how many consecutive losses must I survive with room left to trade?
A defensible answer is 12 to 20. Below 10 you're one ordinary streak from failure. Above 25 the profit target usually becomes unreachable inside the time limit.
Risk per trade ($) = Usable drawdown ($) ÷ Streak to survive
Worked on a $100,000 account with a 5% maximum drawdown:
| Streak to survive | Risk per trade | As % of account |
|---|
| 10 | $500 | 0.50% |
| 15 | $333 | 0.33% |
| 20 | $250 | 0.25% |
Then size the position from that dollar figure and your stop distance:Position size = Risk per trade ($) ÷ Stop distance (per unit)
The position size calculator and the stop loss and take profit calculator do both steps; the prop firm risk calculator adds the evaluation rules on top.
Reduce usable drawdown before you divide
The headline allowance is not what you actually get to use. Subtract:
Costs. Commission and spread on every round turn. Over 60 trades this is a real slice of the allowance — the fee calculator shows how big.
Slippage. If your stops routinely fill 10% worse than the level, your effective risk per trade is 10% higher than planned.
Give-back, if drawdown trails on equity. Profit you let evaporate consumes room.
A buffer. Keep 15–20% of the allowance untouched so a surprise doesn't breach you outright.On a $5,000 allowance, a realistic usable figure is closer to $4,000. Divide that.
Check the target is still reachable
Small risk is only correct if it can still get you to the target in time. Test it:
Trades needed ≈ Profit target ÷ (Risk per trade × Expectancy in R)
With a $4,000 target, $250 risk and 0.35R expectancy: 4,000 ÷ (250 × 0.35) ≈ 46 trades. If your setup appears three times a week, that's about fifteen weeks — fine for an unlimited-time programme, impossible on a 30-day one.
When the arithmetic doesn't fit, change the programme or the strategy. Never the risk.
Fixed fractional vs fixed dollar
Fixed dollar (same risk every trade regardless of balance) is usually better in an evaluation. It's predictable, it makes the streak maths exact, and it doesn't quietly scale you up after a good week.
Fixed fractional (a constant % of current balance) compounds faster but also raises your exposure right after the wins that made you confident.Under a trailing drawdown, fixed dollar is close to mandatory — the floor moves with your balance, so scaling risk with balance leaves your streak tolerance unchanged while the consequences grow.
Scaling: earn it, don't assume it
If you do increase size, tie it to something measurable, not to how you feel:
Only after a fixed number of trades (say 30) at the current size.
Only while the distance to the drawdown floor is above a set threshold.
In increments no larger than 25%.
Reverse immediately if the floor distance drops back below the threshold.Written like that, scaling is a rule. Left unwritten, it's just the confidence that shows up before the streak does.
Common sizing mistakes in evaluations
Using the funded-account size mentality on a challenge. The evaluation has a tighter effective leash than the funded stage on most programmes.
Sizing from the stop that fits the position rather than positioning from the stop the chart justifies. The chart decides the stop; the stop decides the size.
Ignoring correlation. Two positions in instruments that move together is one position at double size. Count them as one for risk purposes.
Increasing size to make up the time limit. The time limit is a constraint on strategy selection, not an excuse for leverage.The summary
Take the allowance, subtract costs, slippage and a buffer, divide by 15, and that's your risk per trade. Then check the target is reachable at that size. If it isn't, the problem is the programme or the strategy — and either of those is cheaper to change than an account.
SimpleAlgo does not sell funded accounts, does not operate an evaluation programme, and has no affiliate relationship with any proprietary trading firm. Nothing here is financial advice, and trading carries a substantial risk of loss. Always read the current rulebook of any programme you join — terms change frequently.
