Fill Rate Calculator

The three fill rates, and why they differ

All three measure the same thing — did the customer get what they asked for — but at different levels of granularity. They will never be equal, and the gap between them tells you something useful.

A worked example

Take the figures pre-filled above — a month at a regional spare-parts warehouse:

• 4,820 lines ordered, 4,180 shipped complete → line fill 86.7%
• 38,400 units ordered, 35,900 shipped → unit fill 93.5%
• 910 orders placed, 648 shipped complete → order fill 71.2%

Line fill is 3.3 points below a 90% target, which sounds like a modest gap. But order fill at 71% means nearly three in ten customers received an incomplete order. The spread between 93.5% unit fill and 86.7% line fill says most shortages are small quantity gaps, not empty bins — so the first move is a min-max review on the shorted SKUs, not a purchase order.

Closing that 3.3-point line-fill gap needs 158 more lines shipped complete in the month. Roughly seven lines a working day. Framed that way it stops being an abstract target and becomes a daily operational goal.

Common mistakes

• Counting a partial shipment as filled. If the customer ordered 10 and received 8, that line is not filled. Some WMS reports default to counting it as filled once the line is closed, which quietly inflates the number by several points.
• Measuring against the revised quantity. When a customer service team reduces an order line to match available stock, the line looks filled. Always measure against the original requested quantity, or you are measuring your own edits.
• Mixing measures between months. A number that jumps because someone switched from unit fill to line fill is a reporting artefact, not a performance change. Fix the definition first, then track the trend.
• Excluding back orders. A line that ships next week was still short this week. Excluding back orders from the denominator is the single most common way fill rate gets overstated.
• Reporting one plant's number as the network's. Weighted by lines, not averaged across sites — a small branch with 200 lines should not move the network number as much as a hub with 5,000.

Questions people ask

What is a good fill rate?

It depends entirely on what you are shipping. Spare parts and after-market operations commonly target 90% line fill, because the catalogue is long-tailed and holding every part is uneconomic. FMCG and pharma distribution usually run 95–98%. E-commerce fulfilment of stocked lines is often 99%+. Comparing your number to another industry's is meaningless; compare it to your own trend and to what your customers are promised.

Should VOR orders be measured separately?

Yes. Vehicle-off-road or emergency lines behave differently from routine stock orders — they are unplanned, urgent, and often for slow-moving parts. Blending them into one number hides both. Track VOR fill and stock fill separately, then report the blended figure only as a summary.

How do I improve it fastest?

Almost never by buying more of everything. Start by classifying the shorted lines: if the same 40 SKUs cause half the misses, the fix is a min-max correction on 40 items, which is a day's work. Buying blanket cover across the catalogue costs a fortune and moves the number less. There is a fuller write-up in raising fill rate without buying more stock.