ISO/IEC 17025 Calibration — Equipment, Validity of Results & Certificates (Clauses 6.4, 7.7, 7.8)
For calibration laboratories, ISO/IEC 17025:2017 centers on three clauses: equipment control (Clause 6.4), ensuring the validity of results (Clause 7.7), and reporting — specifically the detailed requirements for calibration certificates in Clause 7.8.4. This page explains what assessors look for across the calibration scope.
Equipment control — Clause 6.4
Clause 6.4.1 requires equipment and its software to be fit for use and adequately calibrated or verified. Clause 6.4.4 requires a calibration program based on the equipment’s use, and Clause 6.4.6–6.4.9 cover handling, intermediate checks, status identification (the all-important calibration label), and out-of-specification action. For a calibration lab, the reference standards themselves must be traceable (Clause 6.4.3).
Validity of results — Clause 7.7
Clause 7.7 requires the laboratory to have a plan and procedures for monitoring the validity of results — internal quality control such as replicate measurements, control charts, and participation in proficiency testing (Clause 7.7.2). For a calibration lab this is the evidence that measurements stay in control between calibrations.
Calibration certificates — Clause 7.8.4
Clause 7.8.4 lists specific content a calibration certificate must contain: the uncertainty of measurement, the calibration interval, the traceability statement, and any relevant environmental conditions. Missing or vague uncertainty statements are the single most common calibration-lab finding at assessment.
Frequently asked questions
What must a calibration certificate state under ISO/IEC 17025?
Beyond the measured values, Clause 7.8.4 requires the measurement uncertainty, the calibration interval, traceability to national standards, and relevant environmental conditions. Omitting uncertainty is a frequent nonconformity.
What is meant by traceability of reference standards?
Clause 6.4.3 requires reference standards and measuring equipment to be calibrated by a traceable, competent body, with the chain of calibrations linking measurements to an international or national measurement standard.
How often must equipment be calibrated?
Clause 6.4.4 requires calibration intervals based on the equipment, its use and the manufacturer’s guidance. Risk-based intermediate checks between calibrations are part of Clause 7.7 validity monitoring.