Slippage tolerance is the largest price move you are willing to accept between clicking an order and having it filled. In MT4 and MT5 the setting is called maximum deviation, and it does one job: if the fill price has drifted further from your requested price than the number you set, the order is rejected instead of filled. Set it tight and you reject too many orders. Set it loose and you accept bad fills. The whole skill is picking the middle.
What the setting does
Between sending an order and its fill, the price can move. Maximum deviation tells the platform how much of that movement to tolerate. A deviation of 3 pips means "fill me anywhere within 3 pips of my price; beyond that, don't bother." It applies on market-execution accounts, where fills happen at the going price rather than a price you pre-agree.
Most platforms let the deviation cut both ways, but a fill that moves in your favour is never a problem — so the setting really governs how much adverse movement you will swallow.
The trade-off
- Tight tolerance (1–2 pips): you protect your price, but in a fast or thin market your orders get rejected. For an EA, a rejected entry can mean a missed trade; a rejected exit can mean sitting in a losing position you meant to close.
- Loose tolerance (20+ pips): your orders almost always fill, but during news or a gap you can fill far from where you aimed, and the difference is a straight cost.
There is no correct number, only the one that fits how you trade and how much fill certainty is worth to you.
A worked example
Your EA sends a buy on EUR/USD at 1.2500, one standard lot, a pip worth about £8. A news release hits and price jumps 8 pips before the order arrives.
- Deviation set to 3 pips: the 8-pip move is outside tolerance, so the order is rejected. If that was an entry, you missed the trade. If it was a stop-loss exit, you are still holding the loser while it runs.
- Deviation set to 20 pips: the order fills at 1.2508. You paid 8 pips of slippage — about £64 worse than intended — but you are in, or out, as you wanted.
Neither outcome is free. A tight setting cost you a trade; a loose one cost you £64. Which is worse depends entirely on what the order was for.
For exits, most traders run a looser tolerance than for entries. Getting out of a losing position matters more than the last few pips of price, and a stop-loss that keeps rejecting is worse than one that fills a little wide.
Setting it for an EA
Many EAs expose a slippage or deviation input. If yours does, match it to the strategy: a scalper chasing tight edges wants a modest number, while a news or breakout EA needs a wider one so it gets filled when it matters. Test it on the pairs and sessions you trade, not just on a quiet afternoon where nothing slips.
What to check
- The unit. MT4 counts deviation in points, not pips — 30 points is 3 pips on a five-digit broker. Get this wrong and your tolerance is ten times off.
- Entries vs exits. Consider separate settings; the right number is rarely the same for both.
- Your fills over time. If orders reject often, loosen up. If you keep filling wide, tighten.
The Karnek note
Karnek reads the fills your account actually received, so it can show how far they drifted from your intended prices and how often orders slipped. It watches only — read-only, and it can never send an order or change your deviation settings.
Written and reviewed by the Karnek Research team. Last updated August 2026.
Educational content only - not financial advice. Past performance does not predict future results. Trading carries significant risk.