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Confused to Buy NIST, ASTM or OIML Weights?

Updated: Jan 3, 2022


As per our Previous blog, we mentioned How Calibration Weights serves the most integral part of any Laboratory. Its significance of being there to ensure that Lab Balances are giving the accurate readings. We also mentioned what are the short comings if the Lab Balances are not calibrated properly.

However, shifting our focus to Calibration Weights, they are not all made the same. Calibration weights are assigned a class which is based on the accuracy or tolerance of the weight. There are different sets of classes of weights, including ASTM, OIML, and NIST. In addition, there are certifications granted to different weights.

In this guide, we explain the different classes of calibration weights and the certificates that can be purchased alongside them. We also look at other factors to consider when purchasing weights such as style, material, and construction.

Classes of Weights

There are three main calibration weight class systems that you’ll come across:

NIST: National Institute of Standards and Technology (NIST) Class F weights are often used in industrial settings to verify Class III, Class IIII, and non-designated scales. They may also be used in warehouses and manufacturing settings to calibrate scales used for the shipping or production of large products. NIST Class F weights aren’t typically used in laboratories as they are not accurate enough to verify the scales used for most laboratory applications.

ASTM: ASTM International (formerly American Society for Testing and Materials) is a nonprofit non-governmental organization that develops voluntary consensus standards. It has developed 10 calibration weight classes as guided by document ASTM E 617: ASTM Class 000 thru ASTM Class 7. The higher the class number, the higher the level of tolerance (and less accurate) the weight will be. Most laboratory applications require ASTM weights of Class 4 or below. ASTM class weights are the most common type of calibration weights used in US laboratories.

OIML: The Organisation Internationale de Métrologie Légale or International Organization of Legal Metrology (OIML) is an intergovernmental organization that provides standards and systems with the goal of harmonizing legal metrology procedures. From lowest (most accurate) to highest tolerance, the OIML classes are E1, E2, F1, F2, M1, M2, and M3. OIML class weights are more commonly used outside the US and probably all over the Globe.

Certifications of Weights

While looking for calibration weights, you might come across mentions of certifications available for each weight. Indeed, depending on your application, you may require that your calibration weights come with a certificate confirming that the lab testing the weights is accredited. Here are the terms you’ll commonly see and what they’re referring to.

  • ISO/IEC 17025: The International Organization for Standardization (ISO) is an independent non-governmental organization comprising a membership of 164 national standards bodies. The International Electrochemical Commission (IEC) is an international standards organization for electrotechnical fields. Together with other liaison organizations, they created the ISO/IEC 17025 standards. This is the international reference to be used by testing and calibration laboratories that want to display their ability to provide reliable results. In India, all the NABL Calibration Laboratories are accredited to ISO/IEC 17025 standards and Laboratories having such accreditation can only issue valid and authentic Calibration Certificate.

  • NIST/NVLAP: NVLAP refers to a calibration program developed by the National Voluntary Laboratory Accreditation Program (NVLAP) at the (NIST). It provides a means to assess calibration labs for competency, offering accreditation in various fields. It follows the international standard ISO/IEC 17025 (discussed above) when accrediting calibration laboratories. NIST/NVLAP Certificates are most often issued by Calibration Laboratories in US. However, as mentioned earlier, since it follows the International Standard ISO/IEC 17025 customer having any certificate viz, NIST/NVLAP or NABL for India carries the equal weightage and importance.

What do we Provide

We here at V CARE IMPEX, provide all types of Calibration and Laboratory Weight Sets as per OIML R111 Standards only. We have complete range in OIML Weights viz, E1 Class, E2 Class, F1 Class, F2 Class and M1 Class. Also all weights are duly calibrated from ISO/IEC 17025 NABL Accredited Lab. Hence, Weights and certificates supplied by us are universally accepted all over the globe.

We are one of the few companies in India that have in house manufacturing facility to manufacture weights as small as 1 mg to 500 mg and as big as 1 g to 50 Kg.

Lastly, we also provide Calibration services to Calibrate weight sets of our customers and prospective clients.

Should you have any query or requirement please get in touch with us on and can also check our detailed website -

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