Articles · Mike Harty · Published 2026-10-24 · Updated 2026-10-24
Prop Firm Daily Drawdown: How to Size an EA So It Survives
Short answer: The daily drawdown rule fails more EA challenges than the overall limit does. Work backwards: take the firm's daily loss limit in dollars, keep a buffer, decide how many losing trades (or how big a basket) your EA can take in its worst day, and size the lot so that worst day fits inside the buffer.
Key takeaways
- Know which number the firm measures: balance or equity, start of day or high of day, and what "day" means in server time.
- Floating losses usually count. A grid basket can breach the limit without closing a trade.
- Size from the EA's worst day, not its average trade.
- Keep the worst day under about 60% of the daily limit, so spread, slippage and news gaps can't push you over.
All numbers below are illustrative arithmetic: a $100,000 account, EURUSD-style $10 per pip per 1.00 lot. Rules differ between firms. Always check your firm's current terms.
How the rules usually work
| Rule type | What it usually means | Watch out for |
|---|---|---|
| Daily loss limit | e.g. 5% of the starting balance, measured from the day's starting balance or equity | Resets at the firm's server midnight, not yours |
| Static max loss | e.g. 10% below the initial balance, fixed | Floating losses usually count |
| Trailing max loss | The line moves up with new equity or balance highs | Profits shrink your room until the line locks |
| Equity vs balance | Equity includes open P&L | Grid and recovery EAs breach on equity |
Turn the daily limit into a lot size
- Daily limit in dollars: 5% × $100,000 = $5,000.
- Buffer: use 60% of it as your worst-day budget, which is $3,000.
- EA's worst day: from its backtest or signal, the most losing trades (or the deepest basket) in one server day. Say 4 losing trades.
- Risk per trade: $3,000 ÷ 4 = $750, which is 0.75%.
- Lot: $750 ÷ (30-pip stop × $10 per pip per lot) = 2.5 lots.
| Worst losing trades in a day | Risk per trade (60% of a $5,000 limit) | Lot at a 30-pip stop |
|---|---|---|
| 2 | $1,500 (1.5%) | 5.00 |
| 4 | $750 (0.75%) | 2.50 |
| 6 | $500 (0.5%) | 1.66 |
| 10 | $300 (0.3%) | 1.00 |
Lots are rounded down to the 0.01 step. A 30-pip stop on 5.00 lots is $1,500.
Then check the overall limit. A 10% static max loss is $10,000. With a worst multi-day run of 8 losses at $750, that's $6,000, which is inside the limit. If the EA's worst run is longer, cut the lot again.
Grid and recovery EAs on a challenge
Size them on the basket, not the trade. Their worst day is one long move against the full basket, and floating losses count. Recovery EAs that increase lot size after losses are the hardest to fit, because their worst day is much worse than their typical day. In our backtests of a popular MQL5 recovery EA, the drawdown at 0.85 lots was about 2.5× what scaling the 0.01-lot test predicted. A sizing plan built on small-lot tests can break a daily limit you thought was safe. More in grid and martingale EAs: why smooth equity curves fail.
Day-to-day protection
- Track the right number. Use VRD Insight (free) to watch per-EA results and open exposure, so you know which EA is eating the day's budget. Its drawdown is calculated from closed trades; prop firm limits usually count floating loss too.
- Enforce a hard stop below the firm's line. VRD Guardian ($79) is an equity protector and drawdown limiter. You can set a daily loss limit tighter than the firm's, plus news and risky-day windows to pause around events. Guardian makes a best-effort attempt to limit losses and protect an account in difficulty using predefined rules. It cannot guarantee that losses will be avoided or that an account can be rescued. Gaps, slippage, broker or connectivity failures can prevent rules executing. Trading carries a high risk of loss.
- Size from evidence. VRD Quant ($69) turns a backtest into a suggested lot and abandonment level. For recovery EAs, use a backtest run at your real lot.
- Several EAs on one challenge? They share one daily limit. See running multiple EAs on one MT5 account.
Checklist
- I know whether my firm's daily limit uses balance or equity, and when its day resets.
- My EA's worst day fits inside 60% of the daily limit.
- Its worst multi-day run fits inside the overall limit.
- News and rollover hours are paused or the risk is reduced.
- A hard stop sits below the firm's line.
Start free: VRD Insight
Begin with VRD Insight, the free per-EA tracker for MT5, sold through the MQL5 Market. It splits your results by magic number so you can see which EA is earning and which is costing you (drawdown is calculated from closed trades). When you need more: 1. VRD Guardian ($79 or $25/month): loss limits per account and per EA. 2. VRD Quant ($69 or $20/month): turns a backtest into a capital plan. 3. VRD Complete ($149 or $35/month): all three, plus EA Passports and a central reserve.
Related reading
- How much capital do you really need to run an EA?
- Running multiple EAs on one MT5 account
- Grid and martingale EAs: why smooth equity curves fail
- How we review EAs
Risk disclaimer: Trading forex and CFDs with leverage carries a high risk of loss. Prop firm rules vary and change. Check your firm's current terms. Examples are illustrative arithmetic, not forecasts or advice. Passing a challenge isn't guaranteed, and no tool can guarantee to prevent a breach.
Frequently asked questions
How is prop firm daily drawdown calculated?
It varies by firm. Most set a daily loss limit as a percentage of the starting balance, measured from the balance or equity at the start of the trading day (server time). Many count floating losses, so an open trade can breach it before it closes. Always read your firm's exact rule.
Do floating losses count towards daily drawdown?
At many firms, yes: the limit is checked against equity, not just closed balance. That matters most for grid and recovery EAs, which hold large floating losses.
What is the difference between static and trailing max drawdown?
A static limit stays fixed at a level below the starting balance. A trailing limit moves up as the account makes new highs, so profits raise the line you mustn't cross.
How much should an EA risk per trade on a prop challenge?
Work back from the daily limit. Decide the worst number of losing trades in a day, keep that total below about 60% of the daily limit, and divide. For many EAs that comes to 0.25-0.5% per trade, not 1-2%.
Are grid or martingale EAs allowed on prop firms?
Rules differ and change. Some firms restrict certain strategies. Even where allowed, a basket's floating loss can breach a daily limit in one move, so size from the full basket. Check your firm's current terms.
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