Calibration Management: Intervals, Out-of-Tolerance Results and Audit Evidence
When a scale fails calibration, the real question is what it touched since the last good result. Build the programme to answer that.
In Short
- List every instrument that affects quality, with range, tolerance and interval.
- Record as-found results; they drive the impact assessment.
- Change intervals only with documented history.
Calibration & Asset Control Buyer Guide
A 15-page guide to calibration you can defend: the register, status, as-found and as-left, traceability and the impact review after an out-of-tolerance reading.
- Build a register you can defend.
- Work through an out-of-tolerance impact review.
- Keep calibration and maintenance distinct.
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UltimateFree guide
Calibration & Asset Control Buyer Guide
A 15-page guide to calibration you can defend: the register, status, as-found and as-left, traceability and the impact review after an out-of-tolerance reading.
A calibration programme makes sure the scales, gauges, sensors and instruments used to make and test product measure correctly, and that you know what to do when one does not. Audit findings here are concrete: an overdue instrument, a missing certificate, a result with no traceability or an out-of-tolerance result with no impact assessment. This guide covers what a programme includes, where the requirements come from, how to set intervals and tolerances, how to handle out-of-tolerance results and how to choose between in-house and external calibration.
What a calibration programme covers
An inventory of every instrument that affects product quality or a regulated decision, each with a unique ID and location. For each: the range used, the tolerance required, the calibration method or procedure, the interval, the reference standards used and their traceability, and the status (in use, due, overdue, out of service).
Reading a Calibration Record
Sample identifier: BAL-07 · 0–5 kg · ±2 g · as-found +3 g · as-left +0.5 g
Unique ID on the instrument and in the inventory.
More on what a calibration programme covers
Records of every calibration with as-found and as-left results. A procedure for out-of-tolerance results. Labels or status at the point of use so people can see whether an instrument may be used.
The requirements behind it
For US drugs, 21 CFR 211.68 covers calibration of automatic, mechanical and electronic equipment, and 211.160(b)(4) covers laboratory instruments. For US devices, ISO 13485:2016 clause 7.6 (through the QMSR, effective 2 February 2026) requires monitoring and measuring equipment to be calibrated against standards traceable to national or international standards.
More on the requirements behind it
Supplement makers have requirements in 21 CFR 111.27. ISO 9001:2015 clause 7.1.5 covers measurement traceability. Calibration laboratories can be accredited to ISO/IEC 17025; accreditation is a choice you make for suppliers, not a universal legal requirement.
Setting Intervals and Tolerances
Start from how the measurement is used: the product or process tolerance, the risk if the reading is wrong, and the instrument's history. A useful rule of thumb is that the instrument's uncertainty should be small compared with the tolerance it checks.
More on setting Intervals and Tolerances
Begin with the manufacturer's recommendation, then shorten intervals for instruments that drift or are found out of tolerance, and lengthen them only with documented history. Record the reason for every interval change.
When an instrument is out of tolerance
Take the instrument out of use and label it. Record the as-found result.
Worked Example: BAL-07 Found Out of Tolerance
- 14 JunAs-found +3 g against ±2 g; balance labelled out of serviceTechnician
- 14 JunRecords show last good calibration 14 Mar; 11 batches weighed sinceQA
- 16 JunError compared with each formula tolerance; 9 unaffected, 2 heldQA
- 18 JunRetests on 2 batches within specification; QA signs release decisionQA manager
- 20 JunInterval shortened from 3 to 2 months; reason recordedMetrology lead
More on when an instrument is out of tolerance
Then assess impact: which batches, tests or decisions used the instrument since its last good calibration, and whether the error could have affected product quality. Decide and record action, such as no impact with justification, retest, hold or recall assessment, signed by an authorised person. Feed recurring problems into CAPA.
Common Audit Findings
Instruments in use past their due date. Certificates missing as-found data, or with no traceability statement.
More on common Audit Findings
Instruments used outside their calibrated range. Out-of-tolerance results with no impact assessment. Inventory lists that miss instruments found on the floor. Intervals changed without a documented reason. External calibration providers not qualified.
In-House or External Calibration
In-house work needs trained people, written methods, traceable reference standards and controlled conditions. External providers need qualifying like any supplier: check their scope, accreditation where you require it, certificate content and turnaround.
More on in-House or External Calibration
Many sites combine both: routine checks in-house and full calibration by an external laboratory.
Questions
Does every instrument need calibration?
No. Calibrate instruments used for measurements that affect product quality or regulated decisions. Indicators used only for reference can be labelled as not calibrated, with the reason documented.
Is a manufacturer's calibration certificate enough?
It can serve for initial calibration if it shows results and traceability. Ongoing calibration still needs your own schedule and records.
What is the difference between calibration, verification and qualification?
Calibration compares an instrument with a traceable standard and records the error. Verification is a check that an instrument still meets its requirement, such as a daily scale check. Qualification shows that equipment is installed and works as intended for its use.
How long should calibration records be kept?
As long as the records of the products or tests they support, under your regulations and procedures. For US drugs that is linked to batch record retention in 21 CFR 211.180.
Practical orientation, not legal advice. Rules differ by jurisdiction; your quality and compliance team decides what applies.
Keep reading
ICH Q9(R1) Quality Risk Management Guide: Formality, Subjectivity, Decisions
ISO 14971:2019 Medical Device Risk Management Guide
Listeria Environmental Monitoring Guide: Zones, Positives and Records
Medical Device Inventory Management: Manufacturer Controls
OSHA PSM Readiness (29 CFR 1910.119): Elements, Cycles and Management of Change
Recall Management Plan: FDA Food Manufacturing Guide