ISO 17025
ISO 17025 calibration: what it means for your data loggers
Accredited calibration, traceability, and what to check on a certificate.
ISO/IEC 17025 Calibration
Calibration intelligence
for regulated industries
Your sensor data is only as good as its calibration. Practical guidance on what ISO 17025 actually means, what certificates must contain, how often to calibrate, and how to defend your programme to a regulator.
Why it matters
A logger reading 3°C off
is a logger you can't trust
A temperature data logger that hasn't been calibrated against a traceable reference could be reading two or three degrees off — and you'd never know. That means your mapping study, your monitoring alarms and your excursion investigations are all built on unreliable data.
GDP guidelines, GMP Annex 1 and WHO technical reports all require monitoring equipment to be calibrated using equipment with a valid certificate traceable to national standards. ISO 17025 is the international benchmark for calibration-lab competence — and a UKAS-accredited lab is the gold standard for compliance.
The standard explained
What is ISO/IEC 17025?
The international standard for the competence of testing and calibration laboratories. A UKAS-accredited lab has been independently assessed to prove it can produce technically valid, traceable results.
Traceability to national standards
Every certificate must show an unbroken chain back to national measurement standards — in the UK, to the National Physical Laboratory (NPL).
Measurement uncertainty
A valid certificate states the uncertainty at each point. Without it, you can't judge whether a sensor's error is acceptable — a common gap in non-accredited certificates.
Independent accreditation
In the UK, UKAS assesses labs against ISO 17025. If your provider isn't UKAS-accredited, their certificate may not satisfy GDP or GMP inspectors.
What to check
What your certificate
must contain
A GDP or GMP inspector will check each of these. Any gaps are a potential observation.
✓
Unique certificate number & issue date
Enables traceability and version control in your QMS.
✓
UKAS accreditation number of the lab
Verify it at ukas.com — any lab can claim ISO 17025 without being accredited.
✓
Serial number of the instrument
Must match the serial number on the physical logger you deploy.
✓
Calibration points, reference & measured values
Should cover your full operating range — e.g. 2, 8, 15 and 25°C for a pharma warehouse.
✓
Stated measurement uncertainty (k=2)
The most commonly missing item, even from otherwise reputable providers.
✓
Next calibration due date
Or a documented, risk-based justification for your interval.
Calibration intervals — GDP guidance
Temperature sensors (pharma)12 months
Humidity sensors6 – 12 months
CO₂ sensors12 months
Reference standards12 months (UKAS)
After repair or suspected damageRecalibrate now
Intervals should be risk-assessed and documented. These are typical GDP-aligned minimums.
ISO
17025 — the only internationally recognised standard for calibration-lab competence
UKAS
Verify your calibration lab at ukas.com before you use them
12mo
Typical maximum interval for temperature sensors in pharma GDP environments
k=2
Coverage factor on certificates — roughly 95% confidence in the stated uncertainty
Calibration articles
Guides on ISO 17025
& sensor calibration
ISO 17025
How often should you calibrate your temperature sensors?
Intervals, risk-based approaches, and how to justify your frequency to a GDP inspector.
ISO 17025
Measurement uncertainty explained: what k=2 means
A plain-English guide to uncertainty, confidence and compliance decisions.
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