What Are Calibration Weights & Do I Need Them?

Do you need to invest?

Test weights or calibration weights are used to check the calibration of your weighing scales and balances

Test weights or calibration weights as they are also known are precision milled blocks of brass or stainless steel or even cast steel, and they are used to check the calibration of your weighing scales and balances. Test weights are available from 1mg (milligram) up to 20 kg (kilograms) and are available in numerous accuracies depending on the accuracy of the balance you are going to calibrate.

OIML (Organisation Internationale de Métrologie Légale or the International Organisation of Legal Metrology) classes test weights by 3 accuracy classes – E, F and M, and each class is then reduced to further accuracy breakdowns dependant on the application for the weights. Please see OIML chart below for the 5 main classes in use:

Class Use
E1 Test weights for a high degree of accuracy. For use on very high resolution balances with greater than 1,000,000 divisions. 
E2 Most accurate test weights for checking high resolution balances, with a resolution greater than 100,000 divisions and in verification class I.
F1 Test weights for use on analytical and precision balances up to 100,000 divisions and in verification class I or II.
F2 For use with precision balances with up to 30,000 divisions in verification class II.
M1 Test weights for industrial and commercial scales in verification class III and a resolution less than 10,000 divisions.


Having your own test weights allows you to perform periodic checks on your own scales and balances. This is good practice where scales are in constant use, for example on bakery production lines. A daily check would allow QA supervisors to pick up on any calibration faults before the scales were used to weigh hundreds or possibly thousands of products. 

Your own calibration weights will also need regularly calibrating. GNW can offer this service with fast turnaround times, please contact us for more information.