How do you calculate final acceptance test time?

Divide the number of instruments by the test completion rate to get base hours, then multiply by one plus the allowance fraction. For 15 instruments at 1 per hour with a 20 percent allowance, that is 15 hours times 1.20, or 18 scheduled hours.

What is a realistic re-test allowance for instrument FAT?

For mature products 10 to 20 percent is typical; for new or complex instruments with firmware-dependent tests, 25 to 40 percent is safer. The 20 percent default reflects a stable product with occasional re-runs.

Why include a setup and re-test allowance at all?

Because raw throughput ignores fixture setup, warm-up, failed units that need a second pass, and paperwork. Without it your 15-hour base estimate would overrun, which is exactly why the calculator returns 18 hours.

Base test time vs scheduled FAT labor: what is the difference?

Base test time is the ideal hands-on duration assuming everything passes first time (15 hours here). Scheduled FAT labor is what you actually plan and staff for after the allowance (18 hours).

How do I shrink FAT time without cutting coverage?

Raise the effective test rate with parallel benches, automated test sequences, and pre-test burn-in that catches failures earlier, then lower the allowance as first-pass yield improves. Each of those moves a different term in the formula.

Does the allowance cover technician breaks and shift changes?

Only loosely. The allowance is meant for setup and re-test; if your shift has significant non-test downtime, budget that separately or raise the allowance to absorb it.

Lab Equipment & Scientific Instrument Manufacturing calculator

Final Acceptance Test Time Calculator

Final acceptance test (FAT) time estimates the labor hours needed to run a batch of instruments through their full sign-off protocol, including setup churn and re-tests. Test engineers and production planners in scientific-instrument manufacturing use it to size the test cell, schedule technicians, and quote realistic ship dates. It matters because FAT is often the bottleneck of an instrument build: each unit needs warm-up, automated sequences, and manual verification that rarely run first-time-right. Building in an allowance keeps the schedule honest instead of assuming every unit passes on the first attempt.

What this calculator does

Estimate the total labor hours required for final acceptance testing (FAT) on a batch of instruments before shipment. Covers functional testing, performance verification against specifications, environmental stress screening, burn-in, and documentation sign-off. Helps test engineers plan workload and production managers avoid shipping delays from test backlogs.
Use when scheduling FAT for a production batch, estimating test engineer workload for the week, or calculating whether your test team can clear a backlog before the shipping deadline. Critical for instruments requiring multi-hour burn-in, soak tests, or multi-point performance verification.
It computes scheduled FAT labor as the base test time (instruments divided by test rate) scaled up by a setup and re-test allowance.

Formula used

Base test time = instruments to test / test completion rate
Scheduled FAT labor = base test time x (1 + allowance / 100)

Inputs explained

Instruments to test:
Test completion rate:
Setup and re-test allowance:

How to use the result

Use it when planning a test cell for a production batch or quoting lead time that includes the acceptance-test stage.
It assumes a single steady test rate and one blended allowance, so it does not model parallel test benches, learning-curve speed-up, or unusually high failure rates that trigger rework loops.

Current U.S. benchmarks

Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate final acceptance test time? Divide the number of instruments by the test completion rate to get base hours, then multiply by one plus the allowance fraction. For 15 instruments at 1 per hour with a 20 percent allowance, that is 15 hours times 1.20, or 18 scheduled hours.
What is a realistic re-test allowance for instrument FAT? For mature products 10 to 20 percent is typical; for new or complex instruments with firmware-dependent tests, 25 to 40 percent is safer. The 20 percent default reflects a stable product with occasional re-runs.
Why include a setup and re-test allowance at all? Because raw throughput ignores fixture setup, warm-up, failed units that need a second pass, and paperwork. Without it your 15-hour base estimate would overrun, which is exactly why the calculator returns 18 hours.
Base test time vs scheduled FAT labor: what is the difference? Base test time is the ideal hands-on duration assuming everything passes first time (15 hours here). Scheduled FAT labor is what you actually plan and staff for after the allowance (18 hours).
How do I shrink FAT time without cutting coverage? Raise the effective test rate with parallel benches, automated test sequences, and pre-test burn-in that catches failures earlier, then lower the allowance as first-pass yield improves. Each of those moves a different term in the formula.

Last reviewed 2026-05-12.