HB-44 scale tolerance calculator. Class I through IIIL.
Enter the scale's accuracy class, division size, and the applied test weight. Get the NIST Handbook 44 maintenance and acceptance tolerance and the allowed indication range, instantly.
Same tolerance engine that runs inside ScaleForms.
Tolerance is counted in divisions, not pounds.
Handbook 44 expresses scale tolerance as a number of scale divisions that grows with the test load. The calculator divides the applied weight by the division size to get the load in divisions, looks up the allowed divisions for the class, and multiplies back into weight units.
Maintenance tolerance bands
Allowed error for equipment in service, by test load in divisions (d):
| Class | 1d | 2d | 3d | 5d |
|---|---|---|---|---|
| I | 0–50,000d | –200,000d | 200,001d+ | — |
| II | 0–5,000d | –20,000d | 20,001d+ | — |
| III | 0–500d | –2,000d | –4,000d | 4,001d+ |
| IIII (IV) | 0–50d | –200d | –400d | 401d+ |
Class IIIL steps 1 division for each additional 500 divisions of load: 1d to 500d, 2d to 1,000d, and so on up to 20d at 10,000d.
Maintenance vs. acceptance
Maintenance tolerance applies to equipment already in service.
Acceptance tolerance is one half of maintenance and applies to new equipment, equipment returned after repair or reconditioning, and official tests within 30 days of being placed in service.
A truck scale with 20 lb divisions carrying a 20,000 lb test load is at 1,000 divisions: 2 divisions of maintenance tolerance, so ±40 lb in service and ±20 lb on acceptance.
Straight answers.
What is NIST Handbook 44?
NIST Handbook 44 sets the specifications, tolerances, and technical requirements for commercial weighing and measuring devices in the United States. It is adopted by state weights and measures authorities, and commercial scales are tested against its tolerance tables. The current edition is published free by NIST at nist.gov.
What is the difference between maintenance and acceptance tolerance?
Maintenance tolerance applies to equipment already in service. Acceptance tolerance is tighter, one half of maintenance, and applies to new equipment, equipment returned to service after repair, and official testing within 30 days of placing in service.
What accuracy class is my scale?
Class I and II cover precision laboratory and pharmacy balances. Class III covers most commercial bench, floor, and hopper scales. Class IIIL covers large capacity scales such as truck, track, hopper, and livestock scales. Class IIII (IV) covers devices like wheel load weighers used for highway enforcement. The class is marked on the scale's data plate.
Is this an official NIST tool?
No. Handbook44.com is an independent reference tool built by the team behind ScaleForms. It is not affiliated with or endorsed by NIST. Always verify results against the current edition of Handbook 44 and your state's weights and measures requirements.
Your techs shouldn't need this page.
ScaleForms runs this same tolerance math inside every digital test report, automatically, offline, with pass or fail as your techs type. Built for scale service companies.
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