Introduction: why fill rate matters to traders
When you place an order in the forex market you expect it to be executed—either immediately or at a price you specified. Fill rate is a simple but important way to measure how often that expectation is met. For retail traders, fill rate affects how reliably your strategy is implemented: missed fills can mean missed opportunities, partial fills can change position size, and re-quotes or rejects can force you to re-enter trades at worse prices. This article explains what fill rate is, how it’s calculated, what influences it in forex, and what traders can do to monitor and improve it. Trading carries risk; this article is educational and not personalised trading advice.
What “fill rate” means in forex
Fill rate (sometimes called fill ratio or execution ratio) is the percentage of orders—or of ordered volume—that are actually executed by a liquidity provider, broker or exchange. In plain terms it answers two related questions: of the orders you sent, how many were filled? And of the total size you tried to trade, how much was actually traded?
There are two common ways to express it. One approach counts order events: number of orders filled divided by number of orders sent. The other approach measures volume: notional volume executed divided by notional volume submitted. Both are useful but can tell different stories. Counting orders treats a 0.1‑lot fill the same as a 10‑lot fill, while volume-based measures weight large trades more heavily.
How to calculate fill rate (with examples)
Calculating fill rate is straightforward once you decide whether to measure by order count or by volume.
If you use order count, the formula is:
Fill rate (%) = (Number of orders that received at least one fill / Total orders sent) × 100
If you use volume (notional) the formula is:
Fill rate (%) = (Total volume executed / Total volume ordered) × 100
Example 1 — order-count basis:
A trader sends 50 market and limit orders in a session. 45 of those orders are filled (some fully, some partially), and 5 are rejected. The order-count fill rate is (45 / 50) × 100 = 90%.
Example 2 — volume basis:
A trader attempts to buy 10 standard lots across several orders. Only 7.5 lots are actually executed (the rest were rejected or not matched). The volume-based fill rate is (7.5 / 10) × 100 = 75%.
Both examples show situations where fills differ depending on how you measure them. A provider could have a high order-count fill rate but still leave large orders partially unfilled, and vice versa.
Common scenarios: full fills, partial fills, rejects and requotes
When an order leaves your platform it can be handled in several ways. A full fill means the requested size was executed at (or near) the requested price. A partial fill means only some of the size was matched. A reject means the order is refused; a requote is a response offering a different price.
Market orders generally have high fill rates because they match whatever liquidity is available, but they can incur slippage (the executed price differs from the price at order submission). Limit orders only fill if the market reaches your specified price; they can be rejected or simply not filled if price moves away.
Fill or Kill (FoK) and Immediate or Cancel (IOC) order types change behaviour: FoK demands the whole order be filled immediately or cancelled, while IOC will accept any immediate partial fills and cancel the remainder. These order flags affect measured fill rates and are tools traders use to control execution behaviour.
What affects fill rate in forex
A range of market and execution-side factors determine whether orders are filled. Liquidity is central: the amount of counterparties at a price level determines whether an order can be matched without moving the market. Volatility, news events and time of day also influence available liquidity and order matching. The broker’s execution model and the type of liquidity they route to — for example firm, agency, or “last look” counterparties — will change fill outcomes and the frequency of rejections or requotes.
Key factors include:
- Market liquidity and order book depth at the time you trade
- Order size relative to available liquidity (large orders are harder to fill)
- Order type (market, limit, FoK, IOC) and any execution flags
- Volatility and major news releases that widen spreads and remove liquidity
- Broker execution model, internal routing and whether they use last-look practices
- Latency between order submission and execution
These factors interact: a large limit order during a major economic release is much more likely to be partially filled or rejected than a small market order during a calm session.
Execution models and how they change fill behaviour
Not all brokers or liquidity providers behave the same. Some pass orders to electronic communication networks (ECNs) or interbank venues where matching is more deterministic; others use market-making models where the broker may internalise flows. Some venues offer “firm” liquidity that should execute almost every market order when liquidity exists; others apply discretionary checks or last‑look time windows that can lead to fast rejects or requotes.
For example, a firm, central limit order book exchange might show a very high market-order fill rate because trades match visible resting orders. A liquidity provider offering “last look” pricing may provide higher initial quotes but reserve the right to reject trades in a short window for risk checks, which raises reject counts and lowers the simple order-count fill rate.
Retail traders typically cannot see the full venue mechanics, but the practical result is the same: different brokers will produce different fill characteristics for similar orders.
Why fill rate is important for different trading styles
Fill rate matters differently depending on how you trade. Long-term position traders who place infrequent, small orders may rarely be affected by partial fills. Day traders, scalpers and algorithmic systems that rely on precise entry/exit sizes and timing can be exposed if a significant fraction of orders are rejected or partially filled. Execution-sensitive strategies will suffer if the broker has low fill performance for the chosen currency pair, size or order type.
Consider a scalper who needs to enter and exit multiple times per minute with fixed lot sizes; partial fills will change realised position size and profit calculations, and rejects will force the strategy to reprice or miss opportunities. By contrast, a swing trader placing a single 0.1‑lot limit order may be less troubled by a rare reject, though repeated failures over time will still harm results.
How retail traders can monitor and improve fill rate
Traders can take practical steps to understand and, in many cases, improve their effective fill experience. Start by collecting data: use your platform’s trade logs to record attempted orders, filled amounts, execution price, and any reject or requote messages. Run small tests across different times of day and news conditions to see how your broker performs. Compare order-count and volume-based fill metrics to spot whether partial fills are common.
To improve fill outcomes, consider these common tactics:
- Reduce order size or break large orders into smaller tranches to match available liquidity
- Use market orders for fast execution when small slippage is acceptable; use limit orders when price certainty is essential
- Avoid placing large immediate orders during scheduled high-impact news releases
- Choose actively traded pairs and times when liquidity is deep (for example during overlap of major sessions)
- Test alternative brokers or execution accounts to compare execution quality before scaling up
These are general suggestions; each trader must balance execution certainty, slippage, and strategy needs.
Measuring execution quality beyond fill rate
Fill rate is one metric among many used to judge execution quality. It doesn’t capture the price you actually received (fill price) or the cost of having to resubmit rejected orders. Traders and institutions often combine fill rate with slippage statistics, time‑to‑fill (latency) and reject-hold times to build a fuller picture. For larger or algorithmic trading operations, Transaction Cost Analysis (TCA) compares expected and realised outcomes and can convert reject and slippage patterns into an effective cost per trade.
For a retail trader, simple monitoring of fill rate plus average slippage and the frequency of requotes will usually give a clear signal about whether a broker is executing in line with expectations.
Risks and caveats
Fill rate is a helpful but incomplete indicator. A high order-count fill rate can mask poor volume execution if most orders are tiny, while a high volume-based fill rate can hide a large number of small rejections that disrupt a trading strategy. Reported reject messages are not always standardised: different platforms and liquidity providers use different reason codes, and those messages can be ambiguous. Practices like “last look” are permitted by some liquidity providers and can increase fast rejects; other venues avoid that practice but may have different spread behaviour.
Also remember that chasing perfect execution can be costly. Insisting on zero slippage by only using tight limit orders may produce many rejections and missed trades. Conversely, accepting market orders to maximise fill rate can increase slippage, especially in thin markets. Finally, execution behaviour can change over time: a broker that performs well in one month may show different characteristics under stress or after internal routing changes.
Trading involves risk of loss; monitoring execution is part of risk control but does not eliminate market risk. This information is educational and not personalized trading advice.
Practical example — a short case study
Imagine a retail trader who wants to buy 1.0 standard lot (100,000 base currency) of EUR/USD with a limit order at 1.1200. The trader submits one limit order. The market drifts quickly and only 0.6 lots are matched at the limit before price moves away. The remaining 0.4 lots are cancelled. On an order-count basis this single order counted as “filled” (it received at least one fill), so an order-count fill rate metric would mark 100% for that order. On a volume basis the fill rate for that execution is 60% (60,000 / 100,000). If the strategy required a full lot, the partial fill forced a second submission later at a worse price, creating an opportunity cost and possible slippage. Tracking both metrics would help the trader identify whether partial fills are a systemic issue.
Conclusion
Fill rate in forex is the straightforward measure of how much of what you try to trade actually gets executed. It can be counted by order events or by traded volume, and it varies with market liquidity, order type, broker routing and volatility. For execution-sensitive strategies, tracking fill rate alongside slippage and latency gives you a clearer view of real trading costs and performance. Use small tests, log your executions, and consider order sizing and timing to manage execution risk. Trading carries risk and no single metric guarantees profitability.
Key Takeaways
- Fill rate measures how many orders or what fraction of volume you actually get executed; it can be computed by order-count or by volume.
- Market orders tend to have high fill rates but can suffer slippage; limit orders can be rejected or partially filled depending on price movement.
- Liquidity, order size, volatility, and broker execution model are the main drivers of fill performance.
- Monitor fills, slippage and rejects together; test brokers and use order sizing and timing to manage execution quality.
References
- https://www.babypips.com/forexpedia/fill-ratio
- https://www.lmax.com/documents/LMAXExchange-FX-TCA-Transaction-Cost-Analysis-fill-ratio.pdf
- https://www.babypips.com/forexpedia/fill-price
- https://flow.space/blog/fill-rate/
- https://dclcorp.com/blog/fulfillment/fill-rate/
- https://wareiq.com/resources/blogs/fill-rate-in-supply-chain/