How do you calculate parts fill rate?

Divide service part lines filled from stock by service part lines requested, then multiply by 100. With 3,260 of 3,525 lines filled from stock, the parts fill rate is 92.5%.

What is a good service parts fill rate?

Field service operations commonly target 95% or higher to protect first-time fix rates. The example's 92.5% sits 2.5 points below a 95% target, meaning a meaningful share of calls risk a second truck roll.

What's the difference between line fill rate and unit fill rate?

Line fill rate counts how many requested part lines were filled completely from stock; unit fill rate counts the fraction of total units (quantity) filled. Line fill rate is more common in service because a partially filled line still usually fails the repair.

How does fill rate affect first-time fix rate?

They're tightly linked: if the needed part isn't on the truck or in the forward location, the technician can't complete the repair, so a fill-rate miss often becomes a first-time-fix miss and a second visit.

Why is my parts fill rate below target?

Usual causes are thin van stock, demand variability on slow-moving parts, and depot-to-FSL replenishment lag. A 2.5-point gap like the example typically traces to a handful of parts that drive disproportionate misses on common repairs.

How do I improve service parts fill rate?

Stock to demand at the right echelon — deepen van stock on high-frequency repair parts, position critical items in forward stocking locations, and speed depot replenishment. Closing the 2.5-point gap usually means fixing stocking on the top demand-driving SKUs.

Aftermarket, Field Service & Service Parts calculator

Parts Fill Rate Calculator

Parts fill rate is the percentage of service part lines that field service can fill immediately from stock, out of all service part lines requested. In aftermarket and field service, it directly determines first-time fix rate: if the technician doesn't have the part on the truck or in the regional depot, the call gets rescheduled, customer satisfaction drops, and a second truck roll eats the margin. Service parts planners, depot managers, and field operations leaders track fill rate to tune van stock, forward-stocking-location inventory, and depot replenishment against the actual demand technicians generate. It is the link between how you stock service parts and whether your technicians close calls on the first visit.

What this calculator does

Calculate the share of service part demand filled immediately from available stock without backorder or substitution.
a parts inventory analyst needs to measure how well service stock is meeting demand
It computes the share of requested service part lines filled immediately from stock and how that fill rate compares to your target.

Formula used

Parts fill rate = service part lines filled from stock ÷ service part lines requested × 100
Fill-rate gap = parts fill rate - target fill rate

Inputs explained

Service part lines filled from stock: undefined
Service part lines requested: undefined
Target parts fill rate: undefined

How to use the result

Use it per period to evaluate service-parts availability across depots, forward stocking locations, and van stock, and to prioritize which parts to stock deeper.
It measures line availability, not first-time-fix outcomes; a part can be in stock but at the wrong location, so pair fill rate with location-level and first-time-fix data.

Common questions

How do you calculate parts fill rate? Divide service part lines filled from stock by service part lines requested, then multiply by 100. With 3,260 of 3,525 lines filled from stock, the parts fill rate is 92.5%.
What is a good service parts fill rate? Field service operations commonly target 95% or higher to protect first-time fix rates. The example's 92.5% sits 2.5 points below a 95% target, meaning a meaningful share of calls risk a second truck roll.
What's the difference between line fill rate and unit fill rate? Line fill rate counts how many requested part lines were filled completely from stock; unit fill rate counts the fraction of total units (quantity) filled. Line fill rate is more common in service because a partially filled line still usually fails the repair.
How does fill rate affect first-time fix rate? They're tightly linked: if the needed part isn't on the truck or in the forward location, the technician can't complete the repair, so a fill-rate miss often becomes a first-time-fix miss and a second visit.
Why is my parts fill rate below target? Usual causes are thin van stock, demand variability on slow-moving parts, and depot-to-FSL replenishment lag. A 2.5-point gap like the example typically traces to a handful of parts that drive disproportionate misses on common repairs.

Last reviewed 2026-05-12.