Withdrawn Checked October 24, 2026
Withdrawn by NCSL International in 2020 in favor of ISO/IEC 17025:2017. Still named in older flowdowns, which should be updated.
What It Covers
Requirements for a calibration system, notably the limit on the probability of false acceptance (2 percent) when equipment is judged in tolerance.
Who It Applies To
Only where an existing contract still invokes it; otherwise ISO/IEC 17025 and ISO 10012 take its place.
Key Requirements
- False-accept risk limited to 2 percent, or test uncertainty ratio of at least 4:1 where risk cannot be calculated.
- Traceable calibrations with uncertainty stated.
- Out-of-tolerance evaluation and notification.
What an Auditor Asks to See
- How your calibration supplier controls false-accept risk, if the contract still cites Z540.3.
Where Systems Fall Short
- Purchase orders that still require Z540.3 from calibration suppliers who no longer reference it.
How QES Helps
Flowdown updates to ISO/IEC 17025, with decision rules that preserve the risk control Z540.3 was cited for.
Related Standards
Sources. NCSL International (opens in a new tab). Status checked October 24, 2026. This page summarizes ANSI/NCSL Z540.3; it does not reproduce or replace it. Buy the standard from its publisher, or read the regulation in its official text, before relying on a detail. Not legal advice.