What is fill rate?
Fill rate is the percentage of customer demand you ship complete from available stock on the first attempt, without backorders, split shipments or cancellations. It is one of the main KPIs for stock availability and customer service in eCommerce, wholesale and retail supply.
Core principle: Fill rate measures whether you had the right stock when the customer ordered. Low fill rate means lost sales, split parcels and unhappy customers or retailers.
Fill rate formula
Fill rate = (quantity shipped complete on the first shipment ÷ quantity ordered) × 100
Example: Customers order 2,000 units in a week. You ship 1,920 from stock straight away, and 80 go on backorder. Unit fill rate = 1,920 ÷ 2,000 × 100 = 96%.
Types of fill rate
| Type | Measures | Strictness |
|---|---|---|
| Order fill rate | Orders shipped fully complete ÷ all orders | Strictest: one missing item fails the whole order |
| Line fill rate | Order lines shipped complete ÷ all order lines | Medium |
| Unit (item) fill rate | Units shipped ÷ units ordered | Most forgiving |
| Case fill rate | Cases shipped ÷ cases ordered | Common in wholesale and retail supply |
The same week can look very different: 98% unit fill rate can still mean only 90% of orders were complete. Always say which fill rate you mean, especially in contracts with retailers, who often fine suppliers below an agreed level.
Fill rate vs related KPIs
- Perfect order rate: stricter: the order must be complete, on time, undamaged and correctly invoiced.
- OTIF (on time, in full): combines fill rate with on-time delivery, widely used by retailers.
- Stock-out rate: how often a product is unavailable, which drives fill rate down.
How to improve fill rate
- Set reorder points and safety stock per SKU, based on demand and real lead times.
- Sync stock in real time between your shop, marketplaces and warehouse, so you don’t sell what you don’t have.
- Keep fast sellers close to customers, and split stock across warehouses if you sell in several countries.
- Count stock regularly to keep system and shelf in line. See wall-to-wall inventory.
- Track fill rate per SKU and per supplier to find the products that cause most gaps.
Frequently asked questions
What is a good fill rate?
Many brands aim for 95% or more, and retailers often set 95–98% in supplier agreements. The right target depends on your margins and how costly a lost sale is.
How do you calculate fill rate?
Divide the quantity shipped complete on the first shipment by the quantity ordered, and multiply by 100.
Is fill rate the same as service level?
They are related. Service level is often used for the probability of not running out during a replenishment cycle; fill rate measures how much demand was actually met from stock.
