Parts fill rate
What is parts fill rate: parts fill rate explained
Parts fill rate is the share of parts demands a dealership parts department fills immediately from its own stock, expressed as a percentage of everything demanded. It answers one question for the workshop: when a technician asks for a part, how often is it already on the shelf behind the counter?
You will hear it called first-pick fill rate, first-time fill rate, off-the-shelf fill rate, or "level of service", which is the term the NADA guide uses. They all describe the same measurement taken at the counter.
How is parts fill rate calculated?
Parts lines filled from stock on first demand, divided by total parts lines demanded, times 100.
- Count demands, not orders. A single repair order asking for six parts is six demands. Counting jobs instead of lines flatters the number, because one missing line still stops the job.
- Count what was asked for, including what you did not have. This is where most departments lose the plot. A demand that was never recorded because nobody logged the miss simply vanishes from the denominator.
- Fix the window. First-time fill is measured at the moment of demand. Same-day fill allows an emergency purchase or a run to a nearby dealer to land before the technician needs it.
The NADA Management Series guide Parts Checkup: Performance Level Analysis puts the 20 Group performance level at 90 percent first-time fill rate and 95 percent same-day fill rate, and defines level of service as the parts department's ability to supply parts on demand and off the shelf, which "should regularly fall between 90 and 95 percent".
Parts fill rate explained: a worked example
A parts department logs 4,000 demands in a month and fills 3,420 straight off the shelf. First-time fill rate is 3,420 divided by 4,000, or 85.5 percent, which is four and a half points under the 90 percent guide.
Of the 580 misses, 390 became special orders, 150 became emergency purchases from a nearby dealer, and 40 were lost sales the customer took elsewhere. Same-day fill including the emergency purchases is 3,570 of 4,000, or 89.3 percent. The gap between those two numbers, 3.8 points, is the part of the month the department bought its way out of.
How emergency orders hide a bad fill rate
The same-day number is the one that gets reported upward, and it is the one that lies. NADA defines an emergency purchase as "any part purchased at any time, in any quantity, from any source, in any dollar amount, where part or all of the profit that is expected to be earned upon the sale of the part has been spent in the acquisition of the part". You still filled the job. You gave up the margin to do it.
Lost sales are the other half of the honest picture, and they are the harder half. NADA's own DMS goals list expects 3 to 5 lost sales recorded per person per day. A department reporting zero lost sales is not perfect. It is not recording.
Order mix is the third tell. The NADA performance level for order efficiency is roughly 80 percent stock order, 15 percent special order, and 5 percent unit down or critical. A department running special orders at 30 percent is buying reactively, and its fill rate will sit stubbornly in the eighties no matter how much stock it adds.
Why chasing fill rate creates obsolescence
You can hit any fill rate you like by buying enough stock. The bill arrives later, in a bin nobody opens.
- The obsolescence target. NADA's DMS goals put parts with no sale in 12 months or more at 5 percent or less of total inventory, and the healthy inventory profile at roughly 75 percent of stock moving inside 3 months, 23 percent at 4 to 6 months, 2 percent at 7 to 12, and nothing beyond 12.
- What that is worth. The average franchised dealership carried 572,382 dollars of parts inventory in 2025 (NADA Data 2025). Five percent of that is roughly 28,600 dollars. A department sitting at 12 percent obsolescence is holding about 68,700 dollars of stock nobody is going to buy.
- Where it comes from. Mostly from your own counter, not from bad ordering. The NADA parts guide states plainly that fifty percent of current obsolescence nationally comes from uninstalled special-order parts, and asks a blunt question in its checklist: are customers notified promptly when their special-order parts arrive?
That last point is the cheapest fill-rate improvement available to most departments. It costs a phone call.
How does parts fill rate differ from parts availability?
The terms overlap and the framing is different. Parts availability is a field-service measure taken at the point of use, on a customer site, where the question is whether the engineer had the part in the van. Parts fill rate is taken at the dealership counter, where the technician is 20 metres away and the part either is or is not on the shelf.
Two other numbers get confused with it inside fixed operations:
- Inventory turn. How many times the stock sells through in a year. NADA's guide gives 4 to 6 true turns and 6 to 8 gross turns. High turn with low fill rate means you are running too thin.
- Stock accuracy. Whether the system's count matches the shelf. You can be perfectly accurate about not having the part.
Fill rate is also a workshop metric wearing a parts department badge. Every miss that becomes a carry-over eats hours out of tomorrow's diary, which is why parts fill rate and service capacity get reviewed in the same meeting or should be.
