Calibration Weights – OIML Certified Test Weights for Scales & Balances
Our calibration weights and test weight sets are precision-manufactured reference masses used to verify and calibrate the accuracy of scales, balances, and weighing instruments. Regular calibration with certified weights is essential for maintaining measurement accuracy, meeting quality management requirements (ISO 9001, GLP), and ensuring compliance with legal-for-trade and regulatory standards.
We stock a comprehensive range of OIML-certified calibration weights from Class E1 — the highest precision class for analytical balances and microbalances — through to Class M1 for industrial scales and trade-approved equipment. Individual weights and complete sets in protective carrying cases are available, covering denominations from 1 mg up to 20 kg and beyond. All weights are manufactured from high-quality stainless steel or brass and are supplied with calibration certificates traceable to national standards.
OIML Weight Classes Available
- Class E1 — ultra-high precision for calibrating microbalances and reference standard balances; tightest tolerances available
- Class E2 — high precision for analytical balances and calibration of F1 weights
- Class F1 — precision weights for laboratory balances and high-accuracy industrial scales
- Class F2 — standard precision for general laboratory and industrial weighing applications
- Class M1 — commercial grade for industrial scales, trade-approved equipment, and general verification
- Calibration weight sets — complete sets in protective cases for comprehensive scale calibration routines
Key Features
- Certified to OIML R111 international standards for recognised, traceable accuracy
- Full traceability with calibration certificates referenced to national measurement standards
- High-quality stainless steel and brass construction for durability and corrosion resistance
- Individual weights and complete sets available to suit calibration routines of all scales
- Protective storage cases for safe handling, transport, and long-term storage
- Suitable for ISO 9001, GLP, and UKAS audit requirements
Common Applications
- Laboratory balance calibration and routine verification in research and QC environments
- Industrial scale calibration for manufacturing, production, and warehouse weighing equipment
- Legal-for-trade scale verification for retail, food, and commercial weighing compliance
- Pharmaceutical dispensing balance calibration for GMP and regulatory compliance
- Educational and training use in laboratory and metrology settings
- On-site scale service and calibration by weighing engineers and technicians
All calibration weights are supplied with calibration certificates traceable to national standards. UKAS-accredited calibration certificates are available on request for applications requiring the highest level of traceability. Browse below to find the right class, denomination, and set configuration for your calibration requirements.
Frequently Asked Questions
What OIML class calibration weight do I need?
The class you need depends on the accuracy class of the scale or balance you are calibrating. As a general rule, the calibration weight should be at least one accuracy class higher than the instrument being calibrated. For example, use Class F1 weights to calibrate a Class F2 balance, and Class E2 weights for Class F1 instruments. Contact our team if you need guidance on selecting the correct class.
What is the difference between a calibration certificate and a UKAS certificate?
A standard calibration certificate confirms the weight has been measured and found to be within OIML tolerance, traceable to national standards. A UKAS-accredited calibration certificate is issued by a UKAS-accredited laboratory and carries formal accreditation recognition — required for some regulated industries, audit purposes, and ISO 17025 compliance. We can supply both on request.
How often should calibration weights themselves be recalibrated?
This depends on usage frequency, handling conditions, and your quality management requirements. For most laboratory and industrial applications, annual recalibration is recommended. High-use weights or those used in regulated environments (pharmaceutical, legal-for-trade) may require more frequent recalibration. Contact our team for a service schedule recommendation.
Can calibration weights be used for legal-for-trade scale verification?
Yes. Class M1 and higher weights are suitable for verifying trade-approved scales used in commercial transactions. For formal legal-for-trade verification by a weights and measures authority, the weights used must themselves carry valid, traceable calibration certification — all weights in our range meet this requirement.
Do you supply individual weights or sets?
Both. Individual weights are available for specific denomination requirements, while complete sets in protective carrying cases are ideal for comprehensive calibration routines covering a full range of denominations. Sets are particularly useful for service engineers and laboratories that calibrate multiple instruments regularly.
