Rules Desk · How it works

How we check the maths

A calculator that’s wrong is worse than no calculator. So don’t take the tools on trust. Here is what each one assumes, what it leaves out, how we test it, and six cases you can type in yourself to try to break it.

How every tool is tested

  1. A second, separate calculation. For each tool we write the maths again from the rule itself, in a separate program, without looking at the page’s code.
  2. The real page, not a copy. A test browser opens the actual page, types into the real boxes, reads the answer on screen, and compares it with the second calculation.
  3. Zero differences, or it doesn’t ship. Every time a tool changes, the checks run again.

Tool by tool

Counts are from the checks as last run, 26 September 2026.

Rule decoder and the home page box

  • Assumes: the line sits your drawdown below your highest balance (trailing) or below your start (static). If you say it locks, it stops at your starting balance.
  • Leaves out: locks set above your start (such as $100 over), and what a payout does to the line. Check those in your firm’s wording.
  • Checked: 25 figures against the separate calculation, 0 differences. The home page box uses the same maths, tested on 40 random accounts, 0 differences.

Evaluation simulator

  • How it works: it plays out 10,000 evaluations. Each trade is a full win (your average win) or a full loss (your average loss), won with your win rate, in random order. It stops at the target, the drawdown, or 60 trading days. Your daily limit ends the day; your consistency rule and minimum days must be met to pass.
  • Leaves out: slippage and fees, trades of different sizes, the swings inside a single trade, losing streaks that are more likely after a loss (real traders tilt; the dice don’t), and drawdowns that lock.
  • So read it as: the odds for a trader who trades exactly like your averages, every day. If your numbers come from 20 trades, the answer is only as good as those 20 trades.
  • Checked: 13 behaviour tests, all passed. Examples: the same inputs always give the same answer; a 100% win rate always passes and 0% never does; a tighter consistency rule lowers the pass rate; static passes at least as often as end-of-day, which passes at least as often as intraday.

What your trades actually prove

  • Method: the 95% Wilson range for a win rate, a standard statistics formula that behaves well with small samples. Break-even win rate = average loss ÷ (average win + average loss).
  • Leaves out: whether your market or your trading has changed. It treats every trade as coming from the same trader.
  • Checked: 31 checks on the live page, 0 failed.

Consistency calculator

  • Assumes: your best day divided by total profit (or by winning days only, if you pick that), with “at most” or “under” wording.
  • Checked: 63 checks, 0 failures, plus 2,869 random accounts cross-checked against a second method, all agreeing.

Payout-day check and Am I ready to size up?

  • Checked: 76 cases and 53 cases, 0 failures each.

Position size, drawdown runway and the Desk

  • Assumes: contracts are rounded down, never up. Point values are the exchange’s (MNQ $2, NQ $20, MES $5, ES $50).
  • Checked: 72 checks on position size and runway, 38 on the Desk, 0 failures.

Journal & Workbook ($39)

  • Checked: the Review tab’s figures against a separate calculation, 0 differences. The example file with 30 made-up trades shows the whole path: the trades you type, what the Journal works out, and what it means.

Try to break it

Six cases where the obvious answer is wrong. Type them into the tool and check you get the same. We ran each one through the live tools on 26 September. These are example rules, not any one firm’s. Check your firm’s own wording.

1. The winning trade that cost you room

$50,000 account, $2,000 intraday trailing drawdown. A trade runs to $800 open profit and closes at $200. In the decoder: highest $50,800, now $50,200.

line $48,800 room $1,400 (not $2,200)

2. Lock or no lock

$50,000 start, $2,000 trailing drawdown, highest $53,000, now $51,000.

locks at start line $50,000 room $1,000 never locks line $51,000 past the line

3. “At most” vs “under”

50% consistency cap, two winning days of $1,000 each, so the best day is exactly 50%. In the payout-day check, switch how the cap is worded.

"at most 50%" Ready "under 50%" Not yet

4. Closed without breaking the daily limit

$50,000 account, $2,000 static drawdown, $800 daily limit. Monday −$700, Tuesday −$750, so you’re at $48,550. In the decoder:

room left $550 real limit Wed $550, not $800

5. Up $3,200, but you can’t ask for $3,000

Starting balance $50,000, balance now $53,200, $500 buffer to leave, $3,000 largest payout. In the payout-day check:

most you can ask $2,700

6. 12 wins out of 20

Average win $300, average loss $250. In what your trades prove:

win rate 60% likely range 38.7% to 78.1% break-even 45.5% verdict not enough to act on

The bottom of the range is below break-even, so 20 trades can’t yet show this makes money.

Your numbers stay with you

Every tool works out its answer in your browser. What you type is never sent to us. You can test it: open a tool, turn off your Wi-Fi, and keep using it. The Desk saves your rules only in your own browser. Like every Shopify store, the site counts page visits, not what you type.

Found a mistake?

Email support@rulesdesk.com with the numbers you typed and what you expected. If the maths is wrong, we fix it and note the fix on this page with the date.

Fixes so far: none reported yet.

Educational material only. Not investment advice. Trading futures involves substantial risk of loss and most people who try it lose money. Check your account rules with your firm; they change.

Free · one page

Prop firm rules checklist

The questions to answer from a firm’s own rules page before you buy an evaluation. Drawdown type, daily limit, consistency, payouts, every fee.

Here it is: download the checklist (PDF). Three short emails follow; unsubscribe any time.

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The other free tools — no signup, nothing sent anywhere

The Desk (new)Write your rules once, then check each trade against them. Yes or no, with the reason.What it has cost you so farEvery evaluation, reset and monthly fee against every withdrawal. The net.Evaluation simulatorTen thousand simulated evaluations on your numbers. How often do you pass?Consistency rule calculatorYour best day is too big a share. How much more, and the day size to stay under.Payout-day checkCan you request a payout yet? Qualifying days, consistency, buffer and limits.Prop firm rule decoderWhere the line that closes your account actually sits, and what open profit costs you.Am I ready to size up?Four checks on your own record. Not yet, hold, or one step up.The one-page rulebookRules specific enough that a trade either followed them or it didn't.Position size calculatorContracts, dollar risk, and the copied-account multiplier.Drawdown runway calculatorHow many maximum-loss days your account can survive.What do your trades actually prove?Your win rate over a small sample is mostly noise. Find out how much.

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We take no referral fee, affiliate commission or rebate from any prop firm, broker or platform. So we never rank firms, and the tools are free to give you the unflattering answer.

The Rules Desk Workbook cover beside the Journal’s Review tab

Where these numbers live the rest of the week · $39

Journal & Workbook

The same arithmetic in a 500-row trade log that keeps score: your win-rate range, break-even, average result per trade, results by setup, and what rule breaks cost you. Plus an 18-page printable workbook.

One spreadsheet, one PDF. Instant download, no subscription.

See what’s in it

Or wait for the full Desk

The free Desk checks each trade against your rules today. The full version reads your record back each week. One email when it opens, nothing else.

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