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Difference Between E1 Class Weights & E2 Class Weights

The International Organization of Legal Metrology is an intergovernmental organisation that was created in 1955 to promote the global harmonisation of the legal metrology procedures that underpin and facilitate international trade.

In simple words, OIML is an International body that sets standards for Legal Metrology, Tolerances for Weights, Weighing equipment, Balances and Weighing Scales.

Based on Tolerances for Weights, Calibrated Test Weights come in a number of different classes such as E1 Class, E2 Class, F1 Class, F2 Class and M1 Class. Of these, M1 Class Weights are considered to be the least accurate and E1 Class Weights being the most accurate of all.

Still there is one question which always prevail in our minds and that is What is the Difference between E1 Class Weights and E2 Class Weights or others?

1. E1 Class Weights are basically not meant for General Laboratory use. These weights are most popularly used by Calibration Laboratories over the world having ISO 17025 Accreditation. These are used as a primary reference for calibrating other reference Standards and weights. In doing so, Stability of the environmental conditions and Smooth handling of Instrument is assured. The Uncertainty is guaranteed to be 1/3 the tolerance.

2. E2 Class Weights are most popularly used for the calibration of high end Weighing Balances and Scales. Weighing balances such as Semi Micro Balance, Micro Balance and Analytical Balance are calibrated using E2 Class Weights or E2 Class Weight Box. These are used as reference standard weights and also for the calibration of laboratory weighing balances.

But then, there are other classes of Standard weights too viz, F1 Class, F2 Class and M1 Class. What about them? For which Balances or scales these are used in Calibration process? What class of weight do you need for your use?

These are some of the random but important questions we have in our mind.

To simplify this, we have tried to tabulate this in the below table wherein it will be easier for you to understand which class of weights are required to calibrate your balance or weighing scale depending upon its accuracy.

Scale Capacity

0.01 mg

0.1 mg

1 mg

10 mg

100 mg

1 g

10 g

100 g

1 Kg

Upto 200 g




200 g - 1 Kg




1Kg - 30Kg






30Kg - 100Kg




Over 100Kg




Also, please refer to the Calibration Weight class Chart to understand tolerance of each and every weight in their respective class.

calibration weight class chart
Download • 160KB

We hope we have tried to cover almost every doubt and confusion related to difference classes of Standard Weights and Calibration Weights. Still, if you have any queries related to same you can always get in touch with our team on

We have decade old experience working with all kinds of weights and hence please do not hesitate to get in touch with us for any technical queries or requirements you have related to same. You can view our Product catalogue here (

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