Fill rate in distribution: how to measure it and why customers notice

Fill rate is the share of what customers order that you actually ship on time. It sounds like a warehouse number. For a supply house, it's also a customer retention number, because every short order is a reason for a contractor to call someone else.

This guide covers the main ways to measure fill rate, why the version most distributors track can hide the problem, and how to focus on the backorders that cost you customers.

Why fill rate is a customer number, not just a warehouse number

Contractors have backup options. HARDI's 2025 research found 83% of HVAC contractors use three or more suppliers. When an order comes up short, the contractor doesn't wait for your truck. They get the missing items from one of those other suppliers.

Most of the time that's a one-time order. But every time it happens, the other supplier gets a chance to be the one with it on the shelf. Do that enough and the line moves for good.

Supply conditions make this worse right now. Border States' October supply chain update noted that larger diameter conduit and pipe "continue to see extended lead times" (tED).

Three ways to measure fill rate

Line fill rate

The share of order lines shipped complete. If a customer orders 10 different items and you ship 9 in full, line fill rate on that order is 90%. This is the version most distributors track.

Order fill rate

The share of orders shipped complete, with every line filled. Using the same example, that order counts as 0% complete, because one line was short.

Unit or dollar fill rate

The share of units or dollars shipped versus ordered. Useful for inventory planning, but it can make a big miss on a small item look minor.

Why line fill rate can look good while customers are frustrated

Line fill rate and order fill rate can tell very different stories. Here's the math.

If each line on an order has a 95% chance of shipping complete, an order with 10 lines ships complete only about 60% of the time (0.95 multiplied by itself 10 times). An order with 20 lines ships complete only about 36% of the time.

So a distributor can report 95% line fill and still short four out of ten of its bigger orders. Those bigger orders usually come from your best contractors.

Measure fill rate by customer, not just by product

Most fill rate reports are organized by product or by branch. That tells you what to stock. It doesn't tell you who you're hurting.

Add one more view: fill rate by account. For your top accounts, track:

• Order fill rate over the last 90 days.
• The items they were shorted on, and how often.
• What they did next. Did the shorted item show up in their next orders, or did it stop?

That last question is where fill rate turns into a retention problem. If a contractor stops buying a line after a backorder, they probably found it somewhere else.

How to improve fill rate where it matters most

You can't stock everything. So focus on the overlap of three things.

1. Your top accounts by spend. A short order hurts more with a customer you can't afford to lose.
2. The items those accounts buy most often. Pull each top account's 20 most frequent items and check how often you've shorted them.
3. Items with long or unreliable lead times. These are the ones to carry extra stock of or order earlier.

Then fix the communication. When you know an item will be short, a rep calling before the truck shows up is very different from the contractor finding out at the job site.

How to check your own data this week

1. Pull order history for the last 90 days with ordered and shipped quantities by line, from Prophet 21, Eclipse or your system's order reports.
2. Calculate line fill and order fill for your top 50 accounts.
3. List every account with an order fill rate under 80% and the items they were shorted on.
4. For each one, check whether they kept ordering those items from you afterward.
5. Have reps call the accounts where a shorted item stopped showing up.

The 80% cutoff is a starting point. Set it based on what your own numbers look like.

Frequently asked questions

What is the difference between line fill rate and order fill rate? Line fill rate measures the share of order lines shipped complete. Order fill rate measures the share of whole orders shipped with every line complete. Order fill rate is never higher than line fill rate, and it is closer to what the customer experiences.

What is a good fill rate for a distributor? It depends on your product mix and how much stock you can carry. The more useful target is your top accounts' most frequently bought items, because that's where a short order is most likely to cost you the customer's future orders.

How do backorders affect customer retention? A backorder gives the customer a reason to buy from someone else. If the item stops showing up in that customer's next orders, the line has likely moved to another supplier.