Prop firm variance calculator

This prop firm variance calculator deals 1,000 accounts on one edge and shows the spread: the range of outcomes, the worst drawdown and the share that blow up anyway. Enter your own win rate, R:R and drawdown allowance.

  • free
  • no signup
  • runs in your browser
One edge, a thousand accounts

Same edge every time. The spread is variance, not skill.

Where the 1,000 accounts finished
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9 accounts in 10 finished between
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What that spread means against a firm’s actual rulesProp firm challenge calculator →

Median result
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Finished down
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Typical worst drawdown
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Bad-luck drawdown
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Blew the drawdown allowance
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Prop firm variance means one edge produces wildly different accounts

Expectancy gives you an average. You never trade the average — you trade one account, and it lands somewhere in a wide range.

That is why the result above leads with the range 9 accounts in 10 land in. Two traders running your exact strategy can finish 100 trades far apart, with no difference in skill.

Variance blows up profitable accounts

Enter your drawdown allowance in R and the simulation stops any account that touches it, exactly as a prop firm would.

Halve your risk per trade and the same allowance becomes twice as many R. That single change moves the failure rate more than any realistic improvement to your win rate does.

Variance narrows with sample size
(wide at 20 trades, narrow by 200)

Raise the trade count and watch the outcome band close around the median. At twenty trades a genuinely positive edge finishes negative often enough to convince you it is broken; by two hundred the band has pulled clear of zero.

Related calculators

Variance is the reason two traders with the same edge get different months. The edge itself is the trading expectancy calculator; the odds it produces against a firm's actual rules are the prop firm challenge calculator. What widens the spread most is risk per trade, and what the spread runs into is the drawdown floor. At the payout end, an uneven month meets the consistency rule.

01

Prop Firm Challenge Calculator

Monte Carlo simulation of your real odds of passing, respecting drawdown, daily loss and the time limit. Not just profit factor.

 02

Trading Expectancy Calculator

Do you have an edge? Turns your win rate and average win/loss into expected value per trade, in R and dollars.

 03

Prop Firm Drawdown Calculator

Static vs trailing drawdown. See exactly where your account gets liquidated.

Common prop firm variance questions

What is variance in prop firm trading?
Variance is the spread of results a single edge produces. Two traders with identical win rates and identical risk will not finish level after 100 trades — one lands near the top of the range and one near the bottom, purely on the order the wins and losses arrived in. Expectancy gives you the average of that range; variance is how wide it is.
Why did I fail with a 55% win rate?
Because a 55% win rate at 1:1 produces losing streaks of six and seven with ordinary regularity. Run this calculator at 55% and a 10R drawdown allowance and a meaningful share of the 1,000 accounts still hit the floor. Nothing went wrong with your trading — the account was sized so that a normal streak could end it.
How many trades before my edge shows up?
Watch the 5th-to-95th band as you raise the trade count. At 20 trades it is wide enough that a positive edge routinely finishes negative; by 200 it has narrowed and the median has pulled clear of zero. That narrowing is the only reason sample size matters.
How do I use this to size an account?
Convert your drawdown allowance into R and enter it. If the share of accounts that blow up is uncomfortable, the fix is a smaller R — halve the risk and the same allowance becomes twice as many R, which moves the failure share far more than any change to your win rate would.