Scale Classification Reference
Scale Class Determination
This reference table helps determine the appropriate scale class based on the verification scale interval (e) and the number of verification scale intervals (n).
| Class | Value of Verification Scale Interval (e) | Number of Verification Scale Intervals (n) |
|---|---|---|
| SI Units | ||
| I | Equal to or greater than 1 mg | 50,000 (minimum) |
| II | 1 mg to 50 mg, inclusive | 20,000 to 100,000 |
| Equal to or greater than 100 mg | 5,000 to 100,000 | |
| III1-2 | 0.1 g to 2 g, inclusive | 100 to 10,000 |
| Equal to or greater than 5 g | 500 to 10,000 | |
| III L2 | Equal to or greater than 2 kg | 500 to 2,000 |
| IIII | Equal to or greater than 0.1 g | 100 to 1,200 |
| U.S. Customary | ||
| III3 | 0.0002 lb to 0.005 lb, inclusive | 100 to 10,000 |
| 0.005 oz to 0.125 oz, inclusive | 100 to 10,000 | |
| Equal to or greater than 0.01 lb | 500 to 10,000 | |
| III L3 | Equal to or greater than 5 lb | 2,000 to 10,000 |
| IIII | Greater than or equal to 0.01 lb | 100 to 1,200 |
| Greater than or equal to 0.25 oz | 100 to 1,200 | |
Special Notes
1 A Class III scale marked "For prescription weighing only" may have a verification scale interval (e) not less than 0.01 g.
2 For crane and hopper scales (other than grain hopper), verification scale intervals (e) shall not be less than 0.2 kg (0.5 lb), with a minimum number of verification scale intervals (n) of 1,000.
3 On multiple range or multi-interval scales, the number of divisions per range independently shall not exceed the maximum specified for the accuracy class.
Class III Hopper Scales used for weighing grain must have a minimum of 2,000 verification scale intervals.
Understanding Scale Classes
Scale classes are designations used to categorize weighing devices based on their accuracy and precision:
- Class I: Highest precision laboratory scales
- Class II: High precision laboratory scales and jewelry scales
- Class III: Commercial scales for general weighing
- Class III L: Heavy capacity scales like vehicle and axle-load scales
- Class IIII: Low precision commercial scales
Related Terms
Verification Scale Interval (e): The value of the scale division for verifying compliance.
Number of Verification Scale Intervals (n): The capacity of the scale divided by the verification scale interval (e).
Accuracy: The closeness of agreement between a measured value and a true value.
Precision: The closeness of agreement between independent measurements.