Why a stop loss can fill worse than planned: slippage and gaps explained
The Farol Markets team · 29 October 2026 · 5 min read · How we write
In short
- A standard stop fills at the next available price, not at your level.
- Weekends, big announcements and thin hours make slippage more likely.
- Size for the bad fill when you hold through those moments.
You placed a stop 30 pips away, sized the trade for that distance, and still lost twice as much. Nothing was "wrong" with the platform. A stop loss is an instruction to close, not a guarantee of a price, and two market facts, slippage and gaps, decide where it actually fills.
Why a stop is not a price guarantee
When price touches a standard stop, the order becomes a market order and fills at the next available price. In a calm market that is usually at or very near your level. In a fast market, the next price may be several pips away. That difference is slippage. It can happen in your favour too, but the losses are the ones that hurt.
A gap is the extreme case: the market opens at a price far from where it closed, with no trades in between. Your stop then fills at the first price after the gap.
When slippage and gaps are more likely
| Moment | Why |
|---|---|
| The weekend | Forex closes on Friday at 17:00 New York time (18:00 in Brasília while the US is on daylight time, 19:00 otherwise) and reopens on Sunday evening. News in between is priced in at the open |
| Major announcements | Rate decisions, inflation and jobs data can move price faster than orders fill |
| Thin hours | Around the daily rollover and late in the US session, liquidity is lower and spreads widen |
Check the exact session times for your city in the market sessions tool.
A worked example
| Item | Value |
|---|---|
| Long EURUSD at | 1.0850 |
| Stop at | 1.0820 (30 pips) |
| Size | 0.20 lots ($2 per pip) |
| Planned loss | 30 × $2 = $60 |
| Monday opens at | 1.0790 |
| Actual fill and loss | 60 pips × $2 = $120 |
Illustrative calculation, not an expectation of results.
The plan risked $60 and lost $120. On a $2,000 account that is 6% instead of 3%, which is why the size in the first place matters most (see Fixed fractional vs fixed lot).
How to plan for it
- Size with a buffer. When holding through a weekend or news, size as if the stop could slip, or reduce the position. Use the lot size calculator with a wider "worst case" stop to see the difference.
- Decide your news rule in advance: flat before major releases, or smaller size.
- Ask about guaranteed stops. Some firms offer a guaranteed stop loss for a premium. Read the conditions in the contract specifications; don't assume it exists.
- Know your last net. If a gap is large enough, negative balance protection decides whether you can owe more than the balance.
In short
A stop closes the trade at the next available price. Weekends, big announcements and thin hours make that price worse more often. Plan the size for the bad fill, not the ideal one.
Questions people also ask
What is slippage?
The difference between the price you asked for and the price you got. It can be positive or negative.
When does forex close for the weekend in Brasília time?
On Friday at 17:00 New York time: 18:00 in Brasília while the US is on daylight time, 19:00 otherwise. Check your broker's exact hours.
Is there a stop that can't slip?
Some firms offer a guaranteed stop loss for an extra cost. Read the conditions in the contract specifications before relying on it.
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