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Inventory & supply chain

Fill rate calculator — line, order and unit fill

Calculate line fill, order fill and unit fill rates plus perfect order rate from shipped versus ordered, and see why the three numbers disagree.

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Short answer

Fill rate is shipped divided by ordered, but there are three of them. Line fill counts order lines shipped complete, order fill counts orders shipped complete, and unit fill counts units shipped. The same shipments gave 92.4% line fill, 79.1% order fill and 96.7% unit fill, because one short line fails a whole order.

Ask three people in the same company what the fill rate is and you will get three answers, all correct. Line fill, order fill and unit fill measure the same shipments against different denominators, and the gap between them tells you something the individual numbers cannot.

Enter what was ordered and what shipped on the first attempt. The calculator returns all three fill rates, perfect order rate, and a check on whether your shortages are concentrated on a few items or spread across the catalogue.

Your numbers

Order lines
lines
lines

In full, on the first shipment.

Orders
orders
orders

Every line in full. One short line fails the order.

Units
units
units

First attempt only — exclude backorder catch-up.

Other perfect-order gates
%
%
%

Invoice, packing list and paperwork right first time.

Result

Line fill rate
92.4%

Order fill 79.1% · unit fill 96.7% — same shipments, three denominators

Order fill rate79.1%
Unit fill rate96.7%
Perfect order rate74.8%
Lines short365
Orders short238
Units short3,220
Unit fill96.7%
Line fill92.4%
Order fill79.1%
Perfect order74.8%
Line fill = 4,455 ÷ 4,820 = 92.4%
Order fill = 902 ÷ 1,140 = 79.1%
Unit fill = 93,180 ÷ 96,400 = 96.7%
Perfect order = 79.1% × 96.2% × 99.5% × 98.8% = 74.8%
Even-spread check: 92.4% ^ 4.23 lines/order = 71.7% vs actual 79.1%
Only 74.8% of orders arrive complete, on time, undamaged and correctly documented — roughly 287 of 1,140 orders fell short somewhere. Order fill of 79.1% beats the 71.7% an evenly spread 92.4% line fill would produce, so the same items are failing on the same orders. That is the easier problem — a short list of items is driving most of the misses.

Everything is computed in your browser. Nothing you type is sent anywhere or stored.

The formula

Line fill = Lines shipped complete ÷ Lines ordered; Order fill = Orders shipped complete ÷ Orders received; Unit fill = Units shipped ÷ Units ordered; Perfect order = Order fill × On time × Damage free × Documents correct
Lines shipped complete
Order lines filled in full on the first shipment. A partial line counts as a miss, not as a fraction.
Orders shipped complete
Orders where every line shipped in full and together. One short line fails the order.
Units shipped
Total quantity shipped against the quantity ordered, across all lines.
On time / Damage free / Documents correct
The other three perfect-order gates, each as a percentage of orders.

All three measure the first attempt against what the customer asked for. If you re-measure after a backorder ships, everything reads high and nothing is learned. Perfect order rate multiplies rather than averages, which is why it always lands below the weakest component.

Worked example

Order lines ordered
4,820
Lines shipped complete
4,455
Orders received
1,140
Orders shipped complete
902
Units ordered
96,400
Units shipped
93,180
On time / damage free / documents correct
96.2% / 99.5% / 98.8%
Result
92.4% line fill · 79.1% order fill · 96.7% unit fill · 74.8% perfect order

4,455 ÷ 4,820 = 92.4% line fill. 902 ÷ 1,140 = 79.1% order fill. 93,180 ÷ 96,400 = 96.7% unit fill. Perfect order rate multiplies order fill by the three quality gates: 79.1% × 96.2% × 99.5% × 98.8% = 74.8%. At 4.23 lines per order, a 92.4% line fill spread evenly would have produced 71.7% order fill — the actual 79.1% says shortages cluster on a small set of items.

Why the three fill rates disagree

Because a miss propagates upward. One unit short on one line makes that line incomplete, which makes the whole order incomplete, but barely moves the unit count. Order fill is therefore always the lowest of the three and unit fill almost always the highest.

MetricNumerator ÷ denominatorBest used forHow it flatters you
Unit fillUnits shipped ÷ units orderedVolume planning and inventory sizingA single unit short on a 5,000-unit line still reads 99.98%
Line fillLines shipped complete ÷ lines orderedItem-level replenishment and buyer accountabilityTreats a rarely-ordered oddment as equal to your top seller
Order fillOrders shipped complete ÷ orders receivedWhat the customer experiencesHardest to game, and the one nobody volunteers in a review
Perfect orderOrder fill × on time × damage free × documents correctBoard-level service reportingNothing — multiplying four gates is unforgiving by design
Report at least line fill and order fill together. One of them alone is always a partial truth.

The clustering check

If line shortages were scattered at random, order fill would be roughly line fill raised to the power of average lines per order. At 92.4% line fill and 4.23 lines per order that predicts 71.7% order fill. The actual number was 79.1%, which is higher — the same items are failing on the same orders.

  • Actual order fill above the predicted figure means shortages concentrate on a handful of items. That is good news: fixing a short list of reorder points recovers most of the gap.
  • Actual order fill below the predicted figure means shortages are spread across many different items and orders. That points at a systemic cause — forecast bias, a supplier on stop, or a receiving backlog.
  • The two roughly equal means shortages are close to random, which usually means safety stock is uniformly too thin rather than misallocated.

Perfect order rate multiplies, it does not average

Four gates at 97% each do not give you 97%. They give you 0.97⁴ = 88.5%. This is why perfect order rate looks brutal next to the component metrics everyone is used to quoting, and why it is the only one of these numbers that reflects what a customer would recognise as a good delivery.

Turning a fill-rate gap into a decision

A fill rate on its own is a scoreboard, not a plan. Price the gap with the stockout cost calculator, then work out what buffer would close it with the safety stock calculator. Those two numbers together tell you which points of fill rate are worth buying and which are not.

Getting the inputs is the usual obstacle: first-shipment quantities against original ordered quantities, by line, with backorders excluded from the numerator. With you ask for it — "lines ordered versus quantity on the first fulfilment, by month, for the last two quarters" — and the query is shown beneath the answer so you can confirm that "complete" means what you think it means.

Frequently asked questions

How do you calculate fill rate?

Divide what shipped by what was ordered on the first attempt. Unit fill uses quantities, line fill uses order lines shipped complete, and order fill uses orders shipped complete. For 4,455 complete lines out of 4,820 ordered, line fill is 92.4%. Always state which of the three you mean when you quote a number.

What is a good fill rate?

It depends which fill rate and which industry. Distributors commonly target 95–98% line fill; make-to-order manufacturers measure on-time-in-full against a promised date instead. Order fill will sit several points below line fill by arithmetic, so a target set on one metric and reported on another guarantees an argument.

What is the difference between fill rate and service level?

Service level is the probability of not stocking out during a replenishment cycle — an input to your safety stock calculation. Fill rate is the proportion of demand actually satisfied, measured after the fact. A 95% cycle service level typically produces a higher fill rate than 95%, because most stockouts are short and partial.

How is perfect order rate calculated?

Multiply the gates: complete × on time × damage free × correct documentation. Four gates at 97% give 88.5%, not 97%. Some definitions add invoiced correctly as a fifth gate. Whichever set you use, keep it fixed, because adding a gate mechanically lowers the number and looks like a service failure.

Should backorders count against fill rate?

Yes. The line did not ship when the customer asked, so it counts as a miss at the first attempt. Track backorders separately as a recovery measure. If you recompute fill rate after the backorder ships you will produce numbers in the high nineties that tell you nothing about the customer's experience.

Why is my order fill rate so much lower than line fill?

Because an order fails if any of its lines is short. With 4.23 lines per order, a 92.4% line fill can only support order fill in the seventies or low eighties. The more lines per order, the wider that gap grows — which is arithmetic, not a collapse in performance.

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