Fill Rate Calculator

How fill rate reflects service performance

Fill rate is a classic supply chain service metric that answers a simple question: how much of what the customer wanted did you ship on the first pass? You can calculate fill rate at the unit level or at the order level. Unit fill rate measures item availability and is common for inventory planning. Order fill rate measures the share of complete orders shipped without shortfall and is common in e-commerce and retail fulfillment. This calculator supports both so you can align the metric with your operational goals.

The calculation itself is straightforward: shipped divided by requested. The value becomes more useful when you interpret it in context. A 98% unit fill rate can still leave a meaningful number of orders short if the remaining 2% are concentrated in high-volume SKUs. Conversely, an order fill rate of 98% may represent thousands of perfect orders if you ship at scale. This is why pairing fill rate with shortfall counts is helpful; it makes the service gap tangible.

Backorders are optional in this calculator because they are not strictly required to compute fill rate, but they are important for understanding customer impact. If backorders are high, the fill rate decline may indicate a systemic replenishment issue rather than a temporary miss. By capturing backordered units or orders, you can quickly compare shipped, requested, and backordered volumes and decide where to focus.

Fill rate should also be interpreted alongside lead time and safety stock. A lower fill rate may be acceptable for slow-moving items, while critical SKUs often require 95–99% service. If you are missing targets, the root cause may be forecast error, supplier reliability, or under-sized safety stock. This tool does not replace those analyses, but it gives you a clear baseline metric to track.

Use the calculator for weekly or monthly reviews, or to compare different fulfillment strategies. For example, you can model how much fill rate improves when you increase safety stock or shorten lead time. Because the tool runs entirely in your browser, you can use real demand data without sharing it.

Formula

Fill rate: Shipped ÷ Requested

Shortfall: Requested − Shipped

Example calculation

If 12,000 units are requested and 11,400 are shipped, fill rate is 11,400 ÷ 12,000 = 0.95, or 95%. The shortfall is 12,000 − 11,400 = 600 units.

FAQs

Is fill rate the same as service level?

Fill rate is one measure of service level. Many companies use it as their primary service KPI.

What is a good target for fill rate?

Targets vary by category; critical items often target 97–99% while long-tail items may be lower.

How do backorders affect fill rate?

Backorders indicate shortfall but do not change the fill rate formula unless shipped is reduced.

Should I measure weekly or monthly?

Use the cadence that matches your planning cycle and demand volatility.

Is this calculator private?

Yes. All calculations run locally in your browser.

How it works

This calculator divides shipped by requested to compute fill rate and summarizes shortfall. All computation is client-side for privacy.

Disclaimer

Fill rate is a planning metric and should be reviewed alongside customer commitments and allocation rules. Validate against your order policy.