Calibration Intervals · 5 min read
How to Set a Calibration Interval (and Defend It)
Auditors do not object to a one-year interval. They object to a one-year interval with no reason behind it. Here is how to set intervals you can actually defend.
Part of our guide to Calibration Intervals & Program Scheduling.
Start from four inputs
A defensible interval balances four things:
- Manufacturer recommendation (a reasonable baseline)
- Stability — how much the instrument type drifts over time
- Usage — heavy daily use vs. occasional reference
- Consequence — what happens if it is wrong when it verifies product
Document the rationale
Whatever interval you choose, record why. A one-line rationale ("manufacturer 12 months; low usage; non-critical — 12 months") turns an arbitrary number into a controlled decision. When the auditor asks "why annual?", you have an answer instead of a shrug. Then review the interval against as-found history — the subject of the next article.
Common questions
Can different instruments of the same type have different intervals?
Yes — usage and criticality differ. A caliper on a critical inspection cell may warrant a shorter interval than an identical caliper used occasionally. Base it on risk and history, and document it.