What is the consistency rule?
Many prop trading firms evaluate traders on consistency, not just total profit. A common form caps the single best day: your largest one-day profit must be no more than a fixed percentage of your total profit. A 40% rule, for example, means that if you made $2,200 in total, no single day can be more than $880.
The rule rewards steady performance and discourages a single lucky trade from carrying an evaluation. Some firms use other forms, such as a minimum number of trading days or a daily loss limit, so always read the rule text for your specific account.
Worked example
Take five days of P&L: +500, +1,200, +300, −200, +400. Total profit is 2,200. The best day is 1,200, which is 54.5% of the total (1,200 ÷ 2,200 = 0.5454…). Against a 40% rule this fails.
To pass, the best day must be at most 40% of total. Required total = 1,200 ÷ 0.40 = 3,000. Extra profit needed = 3,000 − 2,200 = 800. Note that this is extra total profit from future days; adding 800 on a new day also becomes part of the total, so the result is checked against the new total.
Max you can make tomorrow
If tomorrow is a new best day with profit d, the rule needs d ≤ 0.40 × (2,200 + d), so d ≤ 880 ÷ 0.6 ≈ 1,466.67. Any profit at or below that keeps you compliant, and anything above it breaks the rule.
Tips to pass a consistency rule
- Track every day, including losing days; they count toward the total.
- Keep position sizes stable so no single day dominates.
- Once a big day occurs, the rest of the evaluation must grow the total faster than the best day share.
- Re-check the rule in your firm's current documentation before each evaluation.
How the check is done
The calculator adds every daily P&L you enter to get total profit, takes the largest single day as the best day, and divides that by the total to get the best-day share. The status is PASS only when total profit is positive and the best day is at or below the rule percentage of total. With the default example (500, 1,200, 300, −200, 400) the best-day share is 54.5%, so a 40% rule fails.
Common mistakes
- Leaving out losing days. They reduce total profit, which makes the best day a larger share, so omitting them flatters the result.
- Using a rule percentage from memory. Copy the figure from your firm's current rulebook and recheck it before each evaluation.
- Forgetting that a new day changes both the total and the best day. A large new day can fail a rule that the old total passed, which is why the "max tomorrow" line matters.
- Entering account balances instead of each day's profit or loss.
Using the result
If you fail, the "profit needed" line shows how much extra total profit would bring the best day under the limit, assuming the best day stays the same. Profit from later days raises the total, so one more good day can be enough even though the current total falls short. Re-run the numbers after each session rather than planning from a single estimate.
Frequently asked questions
What is a consistency rule in a prop firm?
It limits how much of your total profit can come from one best day, e.g. 40% of total under a 40% rule. Check your firm's current rules.
How do I calculate the profit needed to pass?
Required total = best day ÷ rule %. Extra needed = required total − current total.
Do losing days affect the rule?
Yes. They reduce total profit, which raises the best day's share.
What percentages do firms use?
Values such as 20%, 30%, 40% and 50% appear, but they change. Verify with the firm.