Glossary
What is fill rate? Formula, types and examples
Fill rate: Fill rate is the share of demand you fill from stock at the first attempt, measured by line, by unit or by value.
Fill rate = demand filled from stock at first attempt / total demand x 100
By Roufaida Bouchamha, founder
The definition
Fill rate measures how much of the demand you receive you can serve immediately from stock, without a backorder, a substitution or a split shipment. It is a measure of your own availability: are the parts or products there when someone asks for them?
Three ways to measure it
- Line fill rate: order lines filled completely from stock / all order lines. The most common, because one short line is what the customer or the production order notices.
- Unit fill rate: units shipped from stock / units ordered. More forgiving: a line filled at 95 percent still counts 95 percent of its units.
- Order fill rate: orders where every line was filled / all orders. The strictest of the three.
Choose one, say which one in every report, and keep it the same over time. Two teams using two definitions will argue about numbers that are both correct.
Fill rate vs OTIF
- Fill rate looks at your stock: could you serve the demand when it arrived?
- [OTIF](/resources/glossary/otif) looks at a delivery: did it arrive on the agreed date with the full quantity? You can measure your own OTIF to customers, or your suppliers' OTIF to you.
A low supplier OTIF often shows up a few weeks later as a lower fill rate, once the safety stock that covered the late deliveries is used up.
Illustrative example, not a customer result
A distributor receives 400 order lines in a week. 368 are filled completely from stock, 20 are partly filled and 12 cannot be filled at all. Line fill rate = 368 / 400 = 92 percent. The 20 partial lines asked for 1,000 units and received 700, so a unit fill rate would read higher than 92 percent.
What pulls fill rate down
- Parts that run out before the next delivery: low days of cover against a late or undated supplier order.
- Reorder points set on old lead times (lead-time drift).
- Stock in the wrong place: on hand at another site, on quality hold, or recorded but not found.
- Demand above the average the safety stock was sized for.
How to improve it without adding stock everywhere
Fill rate is usually lost on a small number of items. List the lines you could not fill last month, group them by item, and look at the top of the list: in most cases the same items have low cover and an open order that arrives too late. Fixing their lead times, reorder points and open orders does more than raising stock across the board, which also raises value above target.
How WERISCO helps
WERISCO shows parts that will run short, ranked by days of cover, and flags late or undated supplier orders by severity, with each part's days of cover shown as evidence, from your ERP or your exports. It does not read customer orders today and does not calculate your fill rate; your team decides what to do. Nothing is written back to your ERP.
Questions people ask
- What is fill rate?
- The share of demand filled from stock at the first attempt, measured by order line, by unit or by order.
- How do you calculate fill rate?
- Divide the demand filled from stock at the first attempt by total demand, then multiply by 100. State whether you count lines, units or orders.
- What is the difference between fill rate and OTIF?
- Fill rate measures your stock availability when demand arrives. OTIF measures whether a delivery arrived on the agreed date with the full quantity.
- Is a higher fill rate always better?
- Not at any cost. Raising stock on every item lifts fill rate but also ties up cash. Fix the few items that cause most unfilled lines first.
