What Slippage Really Costs You (And How to Measure It)
Understanding what slippage really costs you is one of the most overlooked parts of managing your trading edge — it's not a fee anyone bills you for, but it quietly shows up in the gap between the price you expected and the price you got. Spreads and commissions are visible and comparable; slippage is invisible unless you go looking for it, which is exactly why most traders underestimate it.
What Slippage Actually Is
Slippage happens when your order fills at a different price than the one you requested or saw on screen at the moment you clicked. It occurs because:
- Prices move between your click and the broker's execution — even by milliseconds, in fast markets.
- Liquidity runs out at your requested price, so the order fills partly or fully at the next best available price.
- Market orders are especially exposed, since they're designed to fill immediately at whatever price is available, not at a guaranteed level.
- Limit orders protect the price but risk not filling at all if the market moves away.
Slippage isn't inherently a broker problem — it's a market mechanics problem. But how a broker routes and executes your orders strongly influences how often you get it, and in which direction. Some brokers publish execution quality stats (fill rate at requested price, average positive/negative slippage); others don't. That's worth checking on the relevant broker pages before you judge a broker purely on its headline spread.
Where Slippage Bites Hardest
Slippage isn't evenly distributed across your trading day. It clusters around specific conditions:
- High-impact news releases — NFP, central bank decisions, CPI prints — where liquidity briefly vanishes and prices gap.
- Market open and close, particularly the illiquid rollover period late in the New York session.
- Low-liquidity pairs — exotics and some crosses — where the order book is thin even in normal conditions.
- Weekend gaps, where the market reopens at a different level than it closed, affecting any pending orders or stops left open over the weekend.
- Fast-moving breakouts, where everyone's orders hit the market at once and price outruns available liquidity.
If your strategy trades around news or holds positions over volatile periods, your slippage exposure is structurally higher than a trader who avoids those windows — regardless of which broker you use. This is a strategy-level decision as much as a broker-level one.
How to Measure Your Own Slippage
You don't need special software to start measuring slippage — your existing trade history has what you need.
1. Export your trade history from your platform (MT4/MT5 report, or your broker's own platform export from IG or similar). 2. Record three numbers per trade: requested price (or the price shown when you placed the order), the actual fill price, and the timestamp. 3. Calculate the difference in pips for each trade: fill price minus requested price, signed positive or negative depending on direction. 4. Average it across at least 30-50 trades — a small sample can be skewed by one bad news-time fill. 5. Split the data by time of day, instrument, and order type (market vs limit vs stop) to see where it concentrates. 6. Convert the average pip slippage into money using your typical position size, so you have a monthly cost figure, not just a pip number.
This is the same logic PipTax's [cost impact](/cost-impact.html) approach uses for spreads and commissions — treat slippage as another line item in your real cost stack, not a separate mystery.
Turning Pips Into Pounds
A small average slippage figure sounds harmless until you multiply it by trading volume. Here's a simple illustration using round numbers, not a specific broker's data:
| Average slippage per trade | Trades per month | Standard lot pip value (major pair) | Monthly cost | |---|---|---|---| | 0.2 pips | 100 | ~£10 | ~£40 | | 0.5 pips | 200 | ~£10 | ~£200 | | 1.0 pip | 300 | ~£10 | ~£600 |
These are illustrative, not broker-specific quotes. The point is the pattern: slippage cost scales with both your average pip loss and your trade frequency. A high-frequency strategy with even modest per-trade slippage can accumulate a meaningful monthly drag — one that won't show up anywhere on your statement as a labelled fee.
Reducing Slippage Without Guessing
You can't eliminate slippage, but you can manage your exposure to it:
- Avoid placing market orders in the seconds around major news releases unless your strategy specifically depends on it.
- Use limit orders for entries where price precision matters more than guaranteed fill.
- Check execution reports if your broker publishes them — look for the percentage of orders filled at requested price versus worse.
- Trade the most liquid sessions for your instrument — for majors, that's typically London/New York overlap.
- Test in a demo or small live account first if you're switching broker or platform, and log real fills before committing full size.
- Ask brokers directly about their execution model (STP, market maker, ECN) since this shapes typical slippage behaviour, though it's not a guarantee of outcome either way.
Comparing Execution Alongside Spreads and Commissions
Spreads and commissions are only part of your real trading cost. What slippage really costs you sits alongside them, and the two interact — a broker with a tighter headline spread but poor execution can end up costing more overall than one with a slightly wider spread and cleaner fills. That's why cost comparison needs to look at the whole stack, not just the quoted price.
Practical next steps:
- Run your own numbers through the [cost audit tool](/audit.html) to see spread and commission costs side by side with your typical trade size.
- Check the [broker comparison pages](/brokers/index.html) for published execution and regulatory details — for example, how Pepperstone or IG structure their order routing — rather than relying on marketing claims.
- Read the [methodology page](/methodology.html) to see exactly how PipTax defines and compares costs, so you're comparing like for like.
- If you're newer to this, the [trading school](/school/index.html) has foundational material on order types and execution that pairs well with this guide.
Slippage will never disappear entirely — it's a feature of live markets, not a broker defect. But once you've measured it, converted it into pounds, and checked it against your broker's published execution data, it stops being a mystery and becomes just another number you manage, like spread or commission.
Key takeaways
- Slippage is the gap between the price you request and the price you actually get filled at — it can help or hurt you, but on average it tends to cost active traders more than they realise.
- You can measure your own slippage using your broker's trade history: compare requested price, fill price, and timestamp for every order.
- Slippage is worst around news releases, at market open/close, and on illiquid or exotic pairs — plan around these windows if you're cost-sensitive.
- Market orders are more exposed to slippage than limit orders, but limit orders carry their own risk of non-execution.
- Small slippage adds up: 0.5 pips per trade across 200 trades a month is a real, measurable drag on returns.
- Use PipTax's cost tool and broker pages to compare execution quality alongside spreads and commissions before choosing where to trade.
Frequently asked questions
- What slippage really costs you compared to spread costs — which is bigger?
- It depends on your trading style. For most retail traders on major pairs, spread and commission are the bigger, more predictable cost. Slippage tends to be smaller on average but far less predictable — it spikes around news and thin liquidity, which is when it can suddenly cost more than the spread itself.
- Is slippage always bad for the trader?
- No. Slippage can be positive (you get a better price than requested) or negative (a worse price). Over many trades, though, studies and broker execution reports commonly show a mild negative bias, especially on market orders during fast markets — which is why it's worth measuring rather than assuming.
- Can I eliminate slippage completely?
- Not entirely if you use market orders. You can reduce it by avoiding high-impact news windows, trading liquid major pairs, using limit orders where appropriate, and choosing brokers with transparent execution stats. But some slippage risk is simply part of trading live markets.
- Do all brokers report slippage the same way?
- No. Reporting quality varies a lot. Some brokers publish execution statistics (percentage of orders filled at requested price, better, or worse); others don't disclose this at all. Check individual broker pages and ask directly if it's not published.
- How many trades do I need to get a reliable slippage measurement?
- Aim for at least 30-50 filled orders before drawing conclusions, and ideally split them by time of day and instrument. A handful of trades can be misleading because one news-driven fill can skew the average.
- Does slippage affect stop losses too?
- Yes. A stop-loss order, once triggered, is typically executed as a market order, so it's just as exposed to slippage as an entry — sometimes more so, since stops often trigger during fast, volatile moves.