Pipette: types, ISO 8655 parts, error limits and calibration intervals

Pipette calibration measures how much liquid a pipette really delivers and how much that amount varies, and compares both with a limit. The reference method is gravimetric: distilled water dispensed onto an analytical balance, each weight converted to volume with the Z factor, then the systematic error (how far the mean is from the set volume) and the random error (the scatter of the deliveries) calculated (ISO 8655-6; VIM 2.17, 2.19). Under ISO 8655-6:2022 a variable-volume pipette is tested at three volumes, at least ten weighings each, with a tip change at each volume (ISO 8655-6, 8.1; Sartorius white paper). Turning the adjustment ring to correct the volume is an adjustment, a separate step (VIM 3.11).

This page is the overview. For the quick check, the equipment, the step-by-step gravimetric method, a worked example and a free calculator, see pipette calibration step by step.

Pipette types

ISO 8655 covers piston-operated volumetric apparatus: pipettes, burettes, dilutors, dispensers and syringes (European Instruments, 2023; SelectScience, 2022). For pipettes, what changes the calibration is:

Pipette	What to know
Fixed-volume	Tested at its nominal volume only (ISO 8655-6, 8.1.1)
Variable-volume	Tested at the nominal volume, 50 % of it, and the lower limit or 10 % of nominal, whichever is greater (ISO 8655-6, 8.1.1)
Multichannel	Tested channel by channel; separate error limits in ISO 8655-2:2022 (Sartorius; ISO 8655-2, foreword)
Electronic (motorized)	Same gravimetric test, with the manufacturer’s speed settings (ISO 8655-6)

Air-displacement pipettes are the subject of DKD-R 8-1, the free German guideline for “piston-operated pipettes with air cushions”. Since 2022, the pipette and its tip are treated as one system, so results are valid only for the tip type used (ISO 8655-2, foreword; SelectScience).

ISO 8655 and the guides that apply

Document	Scope	Access
ISO 8655-1:2022	Terminology, general requirements and user recommendations	Paid
ISO 8655-2:2022	Pipettes: design, adjustment, maximum permissible errors at 100 %, 50 % and 10 % of nominal	Paid
ISO 8655-6:2022	Gravimetric reference measurement procedure	Paid
ISO 8655-7:2022	Alternative procedures, including routine tests	Paid
ISO 8655-8:2022	Photometric reference procedure, up to 5,000 µL	Paid
ISO 8655-10:2024	User guidance, competence, training and suitability	Paid
DKD-R 8-1 (rev. 1)	Calibration of air-displacement pipettes, updated to reference ISO 8655:2022	Free
EURAMET cg-19 (v4.1)	Uncertainty of gravimetric volume calibration	Free
NIST IR 7383-2019 (GLP 10, SOP 14)	Water density and the gravimetric calibration procedure	Free

The parts of ISO 8655 are as summarized by European Instruments (2023) and SelectScience (2022). ISO 8655 describes how to calibrate; ISO/IEC 17025 sets the requirements for the lab that does it (Sartorius; see ISO/IEC 17025 explained).

Error limits

The 2022 edition sets limits at 100 %, 50 % and 10 % of nominal, where the 2002 edition gave them for the nominal volume only and applied the same absolute error across the range (ISO 8655-2:2022, foreword; Eppendorf, 2023). Eppendorf compared both editions: for single-channel pipettes above 100 µL, the limits at nominal volume stayed at 0.8 % systematic and 0.3 % random error, while several small-volume limits changed, most of them tightened (Eppendorf, 2023). We don’t reproduce the 2022 tables, which are not in the free preview; take the values for your pipette from ISO 8655-2 or the manufacturer.

How often to calibrate a pipette

ISO 8655 gives no single interval. Sartorius, summarizing the 2022 edition, lists the factors to weigh: the risk of the application, how often and by how many people the pipette is used, the liquids, the permissible errors you need and the manufacturer’s information (Sartorius). Routine tests should run more often than full calibrations (Sartorius white paper). Older manufacturer documents written for the 2002 edition state a yearly calibration (Eppendorf SOP, 2019, §4), which we could not confirm from the 2022 text. Recalibrate after a drop or a repair, and when a routine check fails; see calibration intervals. If you send pipettes out, the procedure lists what to ask a service, and our certificate guide shows how to review what comes back.

FAQ

What is the difference between a pipette calibration and a routine test?

A calibration under ISO 8655-6 tests a variable-volume pipette at three volumes with at least ten measurements each, under controlled conditions, and states the measurement uncertainty. A routine test under ISO 8655-7, as summarized by Sartorius, can use fewer volumes and at least four measurements per volume, and the uncertainty is optional. Routine tests run between calibrations, at shorter intervals, to catch a pipette that has drifted.

Does ISO 8655 cover multichannel pipettes?

Yes. The 2022 edition of ISO 8655-2 has a separate table of permissible errors for multichannel pipettes, and each channel is tested like a single-channel pipette: a 12-channel pipette at three volumes means 360 weighings. On a single-channel balance all channels aspirate and only the one being measured dispenses into the vessel; a multichannel balance measures all channels in parallel.

Against which limits is a pipette judged?

The calibration measures the systematic and random error; pass or fail needs a limit. That can be the maximum permissible errors of ISO 8655-2, the manufacturer's specification for the model, or tighter limits set by your lab for a critical method. A good certificate says which one it used. The results are valid only for the tip type used in the calibration.