MRO Turn Time (TAT) Calculator for Component Repair Shops
Turn time is the number customers judge a repair shop on, and most of it is waiting, not working. This calculator adds the stages of a typical component repair, shows how many days are hands-on and estimates how many units your shop carries at any time.
Your numbers
From dock to shop induction, including incoming inspection.
Disassembly, cleaning, NDT and findings report.
Time waiting for the customer to approve the repair scope and price.
Average wait for the long-lead parts that stop a job.
Hands-on repair, machining, plating or replacement.
Reassembly and functional test on the bench.
Final inspection and the release certificate.
Your results
A planning aid based on average stage durations. Real turn time varies by unit, work scope and parts availability, so use your own distributions for contract commitments.
Total turn time vs days waiting for parts
Sweeps Waiting for parts from 0 to 60, holding your other inputs fixed.
Want turn time by stage from your ERP?
Tell us which ERP holds your repair orders and we will outline a read-only report that splits turn time into stages.
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How to use the calculator
Enter the average number of calendar days for each stage, using your own data from the ERP or shop system over the last three to six months. Use averages for a first pass, then repeat with the worst quartile to see how bad it gets. The result shows total turn time, the hands-on share and how many days you are over the contract target. The chart sweeps the parts-waiting stage so you can see what each extra day of backorder does to total turn time. If your shop reports turn time in working days, convert before comparing with a contract that uses calendar days.
The method
Total turn time is the sum of the stage durations. The hands-on share is teardown plus repair plus test divided by the total. Work in process comes from Little's law: the average number of units in the system equals throughput multiplied by the average time each unit spends there. A shop completing 40 units a month with a 30 day average turn time carries about 40 units at any moment. Reducing turn time by a week without changing throughput lowers WIP and the cash tied up in it, which is often the faster financial argument.
- Total = receiving + teardown + quote + parts + repair + test + release + shipping
- Hands-on share = (teardown + repair + test) / total
- WIP = monthly throughput x total days / 30
Reading the result
A hands-on share below about a third is common in component repair, and it tells you that waiting dominates. Look first at the waiting-for-parts and quote stages, because they are the least dependent on your own labor. Shortening the quote stage often needs a pre-approved scope or a not-to-exceed price. Shortening the parts wait needs better findings forecasting and stocking of repeat consumables. Adding bench capacity helps little when the units are sitting on a shelf waiting for approval or material.
Common mistakes
The first mistake is measuring from induction instead of from dock receipt, which hides the days before the unit is started. The second is averaging stages that differ by work scope: a simple inspection and a full overhaul should not share one number. The third is ignoring the tail. A shop that averages thirty days but ships a fifth of its units after sixty days will feel late to customers. Run the calculator for each repair family and use percentiles from your data where you can.
Frequently Asked Questions
What is a good MRO turn time?
It depends on the component, the scope and the contract. Simple inspections may be days, while complex overhauls with long-lead parts take weeks or months. Use your contract targets and your own history as the benchmark rather than a general number.
Why does the hands-on share matter?
It shows how much of the elapsed time is actual work. A low share means most of the delay is queueing, approvals or waiting for parts, so adding labor does little. A high share means capacity or process time is the constraint instead.
How is work in process calculated?
It uses Little's law: average units in the system equals the completion rate multiplied by the average time in the system. The calculator uses completions per month and a 30 day month. It assumes a steady state, so use it for planning, not for a daily count.
Should I use calendar or working days?
Use whichever your contract uses, and stay consistent. Most component repair contracts quote calendar days from receipt, but some quote working days. If your inputs come from a system that counts working days, convert them before comparing against a calendar-day target.
If you want turn time by stage pulled automatically from your work orders, we can build a read-only report on your ERP data. Netray works with SAP, Infor, Oracle and other systems on-prem.
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