Calibration Weights

Calibration Weights

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Ohaus Calibration Weights

Q: How often should calibration weights be used?

That depends on usage and environment, but regular checks are recommended, especially for frequently used scales.

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What are Ohaus weights used for?

Calibration weights are essential for maintaining accurate, trustworthy measurements across any weighing operation. Whether you're verifying a scale's performance or performing routine checks, using the right calibration weights helps ensure your equipment stays accurate and compliant. At Scales Galore, we offer calibration weights that support consistent results you can rely on day after day.

ASTM Class 1

	Class 1 Individual
	Class 1 Weight Sets

OIML Class F1

	Class F1 Individual
	Class F1 Weight Sets

OIML Class E2

	Class E2 Individual
	Class E2 Weight Sets

ASTM Class 4

	Class 4 Individual
	Class 4 Weight Sets

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ASTM Class 6

	Class 6 Individual
	Class 6 Weight Sets

ASTM Class F

Class F Individual

Metric Hooked Weights

	Hooked Individual
	Hooked Weight Sets

Metric Slotted Weights

	Metric Slotted Individual
	Metric Slotted Sets

Attachment Weights

Attachment Weights Sets

Ohaus calibration weights and calibration mass sets

Manufactured to international standards (ASTM and OIML), Ohaus loose calibrations weights and calibration mass sets are available in a variety of styles for a wide range of uses.

In addition to the conventional shapes, Ohaus also offers hooked and slotted masses for use in physics. Calibration weights for the continuous accuracy of your electronic balances are available from 1 mg to 50 kg.

Also see

Troemner Calibration Weights

Sartorius Calibration Weights

Rice Lake Calibration Weights

Weights FAQ

What is NIST?

NIST stands for National Institute of Standards and Technology, and is a division of the United States Department of Commerce. The NIST makes regulations that manufacturers must follow to ensure industry standards. When purchasing NIST weights or weight sets you are being assured that your weights have been tested to meet their standards. NIST weights are most commonly used for commercial and legal for trade scales.

What is NVLAP?

NIST also runs the National Voluntary Laboratory Accreditation Program (NVLAP). This program evaluates and accredits laboratories in their respective fields and ensures they meet ISO standards.

What is ASTM?

ASTM stands for American Society of Testing and Materials. The ASTM is an international organization that establishes and develops methods for testing materials. ASTM weights and weight sets are made to the tolerance, construction, finish, and magnetism set by them. ASTM requires that weights be made of one piece (no fillers or air to compensate for small adjustments). ASTM weights are recommended for calibrating other weights or high resolution balances.

What is OIML?

OIML stands for Organization Internationale de Metrologie or better known as The International Organization of Legal Metrology. OIML is an international organization that sets guidelines for legal metrology. (Metrology involves measurement, measurement devices, and procedures.) OIML guidelines encompass everything from how the weights are manufactured to how they are to be used in calibration procedures.

What is a traceable certificate?

Many weights and weight sets are available with traceable certificates as an additional option. These certificates are issued by laboratories and manufacturers that are accredited by NIST/NVLAP, ASTM, and/or OIML depending on the type of weight, manufacturer, and class. These certificates are traceable to NIST and contain information such as type of weight, weight class, density, uncertainty, and environmental conditions at the time of calibration.

What is a certificate of calibration or calibration report?

This report is similar to the traceable certificate however it will have a smaller uncertainty and more precise values. This has to do with the methods involved as well as the number of times the tests are repeated.

What is a traceable mass value report?

This report is traceable to NIST and reports the actual weight values, tolerances, and uncertainties. However the ratios reported are not guaranteed and is not considered an accredited document.

What is a certificate of accuracy?

A certificate of accuracy is not accredited or traceable. This report is required to be completed to NIST standards and will have an NIST report number. This report will contain the weight or weight sets serial number, description, nominal value, class and tolerance.

Do I need a certificate for my weight(s) or weight set(s)?

This depends upon your needs and requirements. You need to check with your governing agency, quality control department, or product literature. Usually if dealing with ISO-9000 requirements you will need some form of an NIST traceable certificate.

How often do I need to have my weight(s)/weight set(s) calibrated?

There is no set industry standard, but it is recommended that it is done annually.

What class weight/weight set do I need?

Class 0, Class 1, E1, E2- These weights are the most sensitive and accurate. These require clean environments and special handling. These classes would be used to calibrate Class I/II balances, balances accurate as 0.001mg, and as a laboratory standard. These classes are considered to be of extra-fine accuracy.

Class 2- This class is considered to have a fine accuracy and designed for Class II balances. This class would be recommended for balances that are as accurate as 1mg.

Class 3- Recommended for analytical balances as accurate as .01g.

Class 4- Recommended for semi-analytical balances accurate to 0.1g. These are ideal for balances in school laboratories and industrial settings.

Class5, Class 6, and Class 7, Class F- These classes would be ideal for industrial and harsh environments. These are most often used for scales used in the home and production settings.

Why Calibration Weights Matter

Ohaus ASTM CLASS 1 Calibration Weight Stainless Steel

Even the most reliable scales can drift over time, and when that happens, the consequences can go beyond a slightly incorrect reading. In regulated industries, inaccurate scales can lead to compliance issues during inspections or audits. In shipping environments, even small weight discrepancies can result in higher carrier charges, billing disputes, or rejected shipments.

Using calibration weights regularly helps ensure your scales are performing as expected, protecting both accuracy and accountability. It's a simple step that supports compliance, reduces costly errors, and helps keep operations running smoothly.

Key Features

Calibration weights are built for precision, consistency, and long-term use. Features include:

Known, accurate mass values for reliable calibration
Durable construction that resists wear
Available in a range of sizes and classes
Suitable for routine checks or formal calibration
Helps extend the accuracy and lifespan of scales
Supports compliance and quality control efforts

Common Uses for Calibration Weights

Calibration weights are used anywhere accuracy needs to be verified or maintained. Common applications include:

Scale calibration and verification
Quality control and assurance programs
Laboratories and research facilities
Manufacturing and production environments
Shipping and receiving operations
Routine maintenance of commercial and industrial scales

A Scale for Every Task

Scales Galore offers weighing equipment suited for a variety of industries, including both common and specialized applications.

Choosing the Right Calibration Weights

What is the right calibration weight for your setup? It depends on how your scale is used and the level of accuracy required. Factors like weight class, material, and capacity all play a role. Some applications only need basic verification weights, while others require higher-precision options for regulated or sensitive environments.

Ohaus ASTM Calibration Mass Set When selecting a portable scale, think about how and where it will be used. Capacity, readability, and durability all matter, especially if the scale will be transported often. Some jobs call for a compact model that fits in a bag, while others need a sturdier option that can handle heavier items in changing environments.
Using calibration weights that match your scale's specifications helps ensure accurate readings and reliable performance over time. When in doubt, selecting the appropriate weight set upfront can prevent headaches later. Please contact us if you need assistance choosing the best calibration weights for your scale.

Calibration Weight FAQs

If you're new to calibration weights or replacing an existing set, these common questions can help guide your decision.

How often should calibration weights be used?

How often calibration weights should be used depends on how and where a scale operates. Scales that are used frequently, exposed to harsh conditions, moved often, or used in regulated or legal-for-trade applications typically need more frequent checks. Light-use scales in stable environments may only need annual verification, while high-use, high-risk, or regulated operations often require monthly, quarterly, or even more frequent calibration. Always start with the manufacturer's recommendations and adjust based on usage, environment, and accuracy requirements.

Do calibration weights need to be certified?

Certified weights are recommended for applications that require traceability, compliance, or higher accuracy.

Can one set of calibration weights work for multiple scales?

In many cases, yes, as long as the weights fall within the capacity and accuracy requirements of each scale.

How should calibration weights be stored?

They should be kept clean, protected, and stored in their case when not in use to maintain accuracy.

Find the Best Calibration Weights for Sale at Scales Galore

Scales Galore offers a range of options to support accurate weighing across many applications. Browse our selection to find calibration weights that match your needs, or contact our team for help choosing the right set to keep your scales performing their best.

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