Fill rate

Fill rate is the percentage of customer demand that was actually fulfilled from available stock. It's the positive-framed counterpart to stockout rate — same underlying data, opposite perspective.

The complication is that "fulfilled" can be measured three ways, each answering a different question.

Three variants of fill rate

Unit fill rate — share of total demanded units that shipped:

Unit Fill Rate = Units shipped / Units ordered × 100

Line fill rate — share of order lines fully filled:

Line Fill Rate = Lines fully filled / Total lines × 100

Order fill rate — share of orders fully filled:

Order Fill Rate = Orders fully filled / Total orders × 100

When each one matters

• Unit fill rate — best for B2B and wholesale, where partial shipments are common. A 90% unit fill rate means most of the demand still got served.
• Line fill rate — best for D2C, where customers expect each item they ordered to arrive. A line that ships partially is still a problem from the customer's perspective.
• Order fill rate — best for omnichannel where the customer-perceived experience matters most. An order that ships in two parts feels worse than one that ships complete, even if the total units are the same.

These metrics get tighter as you move down the list. An order fill rate is always lower than the corresponding line fill rate, which is always lower than the corresponding unit fill rate — because a single missing line drags down both order and line measures, while only the missing units affect unit fill rate.

Worked example

A brand receives 100 orders, totalling 250 lines and 800 units, in a week. Outcomes:

• 90 orders shipped complete; 10 had at least one line short
• 240 lines shipped complete; 10 had partial or zero fulfilment
• 770 units shipped; 30 units couldn't be fulfilled

Calculations:

• Unit fill rate = 770 / 800 = 96.3%
• Line fill rate = 240 / 250 = 96.0%
• Order fill rate = 90 / 100 = 90.0%

The same operational reality scores very differently on the three measures. Orders look worst because a single short line breaks the whole order.

Benchmarks

Realistic targets by channel:

• D2C (line fill rate): ≥98%
• D2C (order fill rate): ≥95%
• Wholesale / retailer-direct (unit fill rate): ≥97%; many large retailers contract for ≥95% with chargebacks below
• B2B with negotiated SLAs: typically 95–99% depending on contract
• Marketplace fulfilment (Amazon, ASOS): typically 98%+ to maintain Buy Box and search ranking

Going from 95% to 98% fill rate looks small but usually requires materially more inventory — the safety-stock cost rises non-linearly as you push towards 100%.

Fill rate vs OTIF

Wholesale buyers often track OTIF (On-Time, In-Full) — both fill rate and on-time delivery in one composite metric. An order shipped complete but late fails OTIF. An order shipped on time but short fails OTIF. Both have to hit for a clean OTIF.

OTIF is harsher than either fill rate or on-time delivery alone, and it's the metric most large retailers use for vendor scorecards and chargebacks.

What changes fill rate

The same drivers as stockouts, viewed from the other side:

• Better forecasting (especially for top sellers) raises fill rate
• Better safety stock sizing raises fill rate
• Faster reorder cycles raise fill rate
• Better allocation between locations raises fill rate
• Tighter integration between marketing calendar and ops raises fill rate (no surprise promos)

The cheapest improvement is usually allocation — making sure the stock is where the demand is — rather than buying more inventory.

When 100% fill rate is the wrong target

A common mistake is treating fill rate as a "higher is always better" metric. It isn't.

• End-of-season run-out on fashion is intentional. Hitting 100% fill rate at the end of a season means you over-bought.
• Discontinued lines. Letting them run dry is the right outcome.
• Long-tail experimentation. A new SKU that's still being tested might rationally have a lower fill rate target while the team learns demand.

The right fill rate is the one that balances service level against the cost of carrying inventory to deliver it. For most consumer brands that lands in the 95–98% range, not 100%.