Test Weights for Balance and Scale Calibrations

Interweigh Systems supplies cast iron and stainless test weights for verifying mass at a very precise level of accuracy in laboratory and industrial applications. Our calibration weights meet or exceed all necessary standards including ASTM, OIML, NIST specifications. We not only provide the highest quality mass calibration service available today, we supply weight accessories to maintain your weights in their original pristine condition. These accessories include everything from transfer carts and carrying cases, to canvas dust covers for large weights and gloves and tweezers for handling weights.

Our ISO Scope of Accreditation and Calibration

Interweigh’s CAN-P-4E & ISO/IEC 17025:2005 Scope of Accreditation and Scope of Calibration & Measurement Capabilities. These documents are in pdf format and require Acrobat 4.0 or higher.)

Scale Calibration Weights

Metrology Calibration

Scale calibration is an absolute necessity for any business that wants to ensure that its industrial scales are both precise and accurate. Precision and accuracy are the two cornerstones of ensuring that commercial transactions are fair and trustworthy. The calibration process is not only necessary for the scales themselves, but for the test weights that are used to calibrate those scales. The science of making sure that both scales and test weights are precise and accurate is called metrology calibration.

Our Mass Calibration Laboratory

Our Mass Calibration Lab is designed and constructed to meet the recommended environmental and procedural practices as detailed in Measurement Canada's Calibration Procedures for Standards of Mass, document # RP-01FIELD.001. In fact our Laboratory exceeds the requirement by including the elevation of our facility into the calculations for Air Density. Our lab has been accredited for mass calibrations by the Laboratory Accreditation Bureau since 2004 and A2LA prior to that. Our laboratory is climate controlled with the Temperature at 20 degrees C and the Humidity between 30% and 50%. The Barometric Pressure is measured to 0.05 mm Hg. The lab is fully enclosed with the internal air Hepa-filtered every 20 minutes to reduce any airborne material. The air conditioner's supply and exhaust air is external from the lab's air thus maintaining a clean air environment. Our Mass Calibration Lab is equipped with granite tables for the lab balances, thus reducing vibrations. It also is equipped with a large anti-static mat on the floor to prevent any static electricity effecting the accuracy of the lab balances. Interweigh only uses Certified Class 1 test weights to perform any Class F calibration verifications. These weights are certified by a NVLAP lab and are Traceable to the NIST Standard.

Test Weights


Our Staff

Interweigh's metrology team has been trained in mass calibrations to meet the guidelines of Measurement Canada's Calibration Procedures for Standards of Mass. They also have extensive experience in mass calibrations participating in Weights and Measures Canada's annual re-certification of Interweigh's own field test weights. Only Certified Calibration Technicians are allowed to supply mass calibrations.

The Calibration Process

This is accomplished through a hierarchical system where each scale is compared against an external reference, known as a standard. Each standard is then tested against a higher level (more accurate and precise) standard, which is compared against an even higher standard, and so on. In Canada the master document describing how Standards of Mass must be calibrated for use in commercial purposes is Measurement Canada's document RP-01Field. This process of comparison against a standard, and making any necessary adjustments, is commonly referred to as calibration. Detailed records are kept for every standard to ensure traceability, and that the scales used for mass calibrations met clearly identified specifications for both accuracy and precision in all its operating parameters. This collaboration between the government and calibrations laboratories ensures the highest achievable standards possible and guarantees fairness in the marketplace.

Interweigh maintains a complete set of Primary Mass Standards directly traceable to NIST. Our Mass Calibration Services include:

  • Calibration "As Found" and "As Left" deviations from the Nominal Value reported for each weight.
  • Cleaning - Foreign contaminants on weights will be removed.
  • Adjustment - If weights are found to be out of tolerance, then the weights that can be adjusted will be (1 piece weights can not be adjusted).
  • Detailed certificate provided with your weights.
  • Fast turnaround time - Class F Industrial Weights - 4 days from arrival at Calibration Laboratory - All other classes - 10-15 days from arrival at calibration laboratory.

Contact us today: Toll Free: 1.800.268.3269 or by Email:

The Ownership and Management - Interweigh Systems Inc. 51 Bentley Street, Markham, Ontario, Canada, L3R 3L1
Phone: (416) 491-7001 ~ Toll Free: (800) 268-3269 ~ Fax: (905) 940-1711

Or contact us at one of our five locations: Markham, Mississauga, Woodstock, Montreal and Calgary