What is Weight Tolerance
By raw definition, weight tolerance is the difference between the maximum and minimum values of a given nominal value. For applications in metrology, weight tolerance tells you how much deviation is allowed in the mass of your weight, while still being considered an accurate representation of that mass.
How to Determine Weight Tolerance
Weight tolerance is determined by the governing bodies that oversee national and international weighing standards. The three primary organizations are: ASTM International (Formerly the American Society for Testing and Materials), OIML (International Organization of Legal Metrology), and NIST (National Institute of Standards and Technology).
Each of these organizations have defined Calibration Weight Classes, which group weights based on how accurate they truly are to their nominal value.
High precision classes like ASTM Class 1 and OIML Class E1 will have very low tolerances, meaning the weight is as close to its true value as possible. Low precision classes like ASTM Class 6, OIML Class M2, or NIST Class F, will have a higher tolerance, meaning your weight is close to its reported mass, but may deviate a little more than a high precision class.
For example, let’s look at a 1 gram weight.
Class | Weight Tolerance | “In-Tolerance” Range |
ASTM Class 1 (1 g weight) | 0.034 mg | 0.999966 g – 1.000034 g |
ASTM Class 6 (1 g weight) | 2.0 mg | 0.998 g – 1.002 g |
As we can see, the ASTM Class 1 weight tolerance is much more precise compared the Class 6. The tolerance range is much more narrow, indicating that the true mass of the Class 1 weight is much closer to a true gram than a Class 6.
The type of calibration weight class you should be using is determined by the class of your scale. For a full breakdown of scale classes, please refer to NIST Handbook 44 (Section 2) or OIML Handbook R76-1, (Section 3.2). You can also read our guide, What are Calibration Weight Classes, to learn more about scale/balance classes and calibration weight classes.
Scale Class vs. Calibration Weight Class Comparison Reference
Knowing your weight tolerance is an essential part of any weight calibration process. If your weight is not in tolerance, you run the risk of affecting your businesses’ processes, and worse, running afoul of federal compliance regulations which may govern your industry. That’s why it’s essential to keep your calibration weights in tolerance.
Weight Tolerance Chart Quick Reference
Weight Tolerance Chart
ASTM E617
Nominal Value | 000 | 00 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
2000 kg |
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| 10 g | 20 g | 40 g | 100 g | 200 g | 300 g |
1000 kg |
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| 5 | 10 | 20 | 50 | 100 | 150 |
500 kg |
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| 2.5 | 5 | 10 | 25 | 50 | 75 |
300 kg |
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| 1.5 | 3 | 6 | 15 | 30 | 45 |
200 kg |
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| 1 | 2 | 4 | 10 | 20 | 30 |
100 kg |
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| 500 mg | 1 | 2 | 5 | 10 | 15 |
50 kg | 13 mg | 25 mg | 63 mg | 125 mg | 250 | 500 mg | 1 | 2.5 | 5 | 7.5 |
30 kg | 7.5 | 15 | 38 | 75 | 150 | 300 | 600 mg | 1.5 | 3 | 4.5 |
25 kg | 6.25 | 12.5 | 31 | 62 | 125 | 250 | 500 | 1.2 | 2.5 | 4.5 |
20 kg | 5 | 10 | 25 | 50 | 100 | 200 | 400 | 1 | 2 | 3.8 |
10 kg | 2.5 | 5 | 13 | 25 | 50 | 100 | 200 | 500 mg | 1 | 2.2 |
5 kg | 1.3 | 2.5 | 6 | 12 | 25 | 50 | 100 | 250 | 500 mg | 1.4 |
3 kg | 0.75 | 1.5 | 3.8 | 7.5 | 15 | 30 | 60 | 150 | 300 | 1 |
2 kg | 0.5 | 1 | 2.5 | 5 | 10 | 20 | 40 | 100 | 200 | 750 mg |
1 kg | 0.25 | 0.5 | 1.3 | 2.5 | 5 | 10 | 20 | 50 | 100 | 550 |
500 g | 0.13 | 0.25 | 0.6 | 1.2 | 2.5 | 5 | 10 | 30 | 50 | 300 |
300 g | 0.075 | 0.15 | 0.38 | 0.75 | 1.5 | 3 | 6 | 20 | 30 | 210 |
200 g | 0.05 | 0.1 | 0.25 | 0.5 | 1 | 2 | 4 | 15 | 20 | 160 |
100 g | 0.025 | 0.05 | .13 | 0.25 | 0.5 | 1 | 2 | 9 | 10 | 100 |
50 g | 0.015 | 0.03 | 0.06 | 0.12 | 0.25 | 0.6 | 1.2 | 5.6 | 7 | 62 |
30 g | 0.014 | 0.026 | 0.037 | 0.074 | 0.15 | 0.45 | 0.9 | 4 | 5 | 44 |
20 g | 0.013 | 0.025 | 0.037 | 0.074 | 0.1 | 0.36 | 0.7 | 3 | 3 | 33 |
10 g | 0.01 | 0.02 | 0.025 | 0.050 | 0.074 | 0.25 | 0.5 | 2 | 2 | 21 |
5 g | 0.005 | 0.01 | 0.017 | 0.034 | 0.054 | 0.18 | 0.36 | 1.3 | 2 | 13 |
3 g | 0.005 | 0.01 | 0.017 | 0.034 | 0.054 | 0.15 | 0.3 | 0.95 | 2 | 9.4 |
2 g | 0.005 | 0.01 | 0.017 | 0.034 | 0.054 | 0.13 | 0.26 | 0.75 | 2 | 7 |
1 g | 0.005 | 0.01 | 0.017 | 0.034 | 0.054 | 0.1 | 0.2 | 0.5 | 2 | 4.5 |
500 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.025 | 0.08 | 0.16 | 0.38 | 1 | 3 |
300 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.025 | 0.07 | 0.14 | 0.3 | 1 | 2.2 |
200 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.025 | 0.06 | 0.12 | 0.26 | 1 | 1.8 |
100 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.025 | 0.05 | 0.1 | 0.2 | 1 | 1.2 |
50 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.042 | 0.085 | 0.16 | 0.5 | 0.88 |
30 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.038 | 0.075 | 0.15 | 0.5 | 0.68 |
20 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.035 | 0.07 | 0.12 | 0.5 | 0.56 |
10 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.03 | 0.06 | 0.1 | 0.5 | 0.4 |
5 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.028 | 0.055 | 0.08 | 0.2 |
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3 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.026 | 0.052 | 0.07 | 0.2 |
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2 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.025 | 0.05 | 0.06 | 0.2 |
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1 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 | 0.025 | 0.05 | 0.05 | 0.1 |
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0.5 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 |
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0.2 mg | 0.002 | 0.003 | 0.005 | 0.01 | 0.014 |
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0.1 mg | 0.002 | 0.003 | 0.005 | 0.01 |
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0.05 mg | 0.002 | 0.003 | 0.005 | 0.01 |
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Weight Tolerance Chart
NIST Handbooks**
Nominal Value | 105-1 F | 44 Accept | 44 Maint |
2000 kg | 200 g |
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1000 kg | 100 |
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500 kg | 50 |
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300 kg | 30 |
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200 kg | 20 |
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100 kg | 10 |
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50 kg | 5 |
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30 kg | 3 |
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25 kg | 2.5 |
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20 kg | 2 | 750 mg | 1500 mg |
10 kg | 1 | 500 | 1000 |
5 kg | 0.5 | 400 | 800 |
3 kg | 0.3 | 250 | 500 |
2 kg | 0.2 | 200 | 400 |
1 kg | 0.1 | 120 | 250 |
500 g | 70 mg | 88 | 175 |
300 g | 60 | 75 | 150 |
200 g | 40 | 50 | 100 |
100 g | 20 | 35 | 70 |
50 g | 10 | 20 | 40 |
30 g | 6 | 15 | 30 |
20 g | 4 | 10 | 20 |
10 g | 2 | 8 | 12 |
5 g | 1.5 | 5 | 10 |
3 g | 1.3 | 4 | 8 |
2 g | 1.1 | 3 | 6 |
1 g | 0.9 | 2 | 4 |
500 mg | 0.72 | 1.5 | 3 |
300 mg | 0.61 | 1 | 2 |
200 mg | 0.54 | 0.8 | 1.5 |
100 mg | 0.43 | 0.5 | 1 |
50 mg | 0.35 | 0.4 | 0.8 |
30 mg | 0.3 | 0.3 | 0.6 |
20 mg | 0.26 | 0.2 | 0.4 |
10 mg | 0.21 | 0.15 | 0.3 |
5 mg | 0.17 | 0.05 | 0.1 |
3 mg | 0.14 | .05 | 0.1 |
2 mg | 0.12 | 0.05 | 0.1 |
1 mg | 0.1 | 0.05 | 0.1 |
*NIST 105-1 Class F tolerances are rounded to two significant figures
Weight Tolerance Chart
OIML R-111
Nominal Value | Class E0* | E1 | E2 | F1 | F2 | M1 | M2 | M3 |
2000 kg |
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| 10 g | 30 g | 100 g | 300 g | 1000 g |
1000 kg |
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| 1.6 g | 5 | 16 | 50 | 160 | 500 |
500 kg |
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| 0.8 | 2.5 | 8 | 25 | 80 | 250 |
300 kg |
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200 kg |
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| 0.3 | 1 | 3 | 10 | 30 | 100 |
100 kg |
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| 160 mg | 0.5 | 1.6 | 5 | 16 | 50 |
50 kg | 12.5 mg | 25 mg | 80 | 250 mg | 800 mg | 2.5 | 8 | 25 |
30 kg |
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25 kg |
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20 kg | 5 | 10 | 30 | 100 | 300 | 1 | 3 | 10 |
10 kg | 2.5 | 5 | 16 | 50 | 160 | 500 mg | 1.6 | 5 |
5 kg | 1.3 | 2.5 | 8 | 25 | 80 | 250 | 800 mg | 2.5 |
3 kg |
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2 kg | 0.5 | 1 | 3.0 | 10 | 30 | 100 | 300 | 1 |
1 kg | 0.25 | 0.5 | 1.6 | 5.0 | 16 | 50 | 160 | 500 mg |
500 g | 0.13 | 0.25 | 0.8 | 2.5 | 8 | 25 | 80 | 250 |
300 g |
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200 g | 0.05 | 0.1 | 0.3 | 1 | 3 | 10 | 30 | 100 |
100 g | 0.025 | 0.05 | 0.16 | 0.5 | 1.6 | 5 | 16 | 50 |
50 g | 0.015 | 0.03 | 0.1 | 0.3 | 1 | 3 | 10 | 30 |
30 g |
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20 g | 0.013 | 0.025 | 0.06 | 0.2 | 0.6 | 2 | 6 | 20 |
10 g | 0.01 | 0.02 | 0.06 | 0.2 | 0.6 | 2 | 6 | 20 |
5 g | 0.008 | 0.016 | 0.05 | 0.16 | 0.5 | 1.6 | 5 | 16 |
3 g |
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2 g | 0.006 | 0.012 | 0.04 | 0.12 | 0.4 | 1.2 | 4 | 12 |
1 g | 0.005 | 0.010 | 0.03 | 0.1 | 0.3 | 1 | 3 | 10 |
500 mg | 0.004 | 0.008 | 0.025 | 0.08 | 0.25 | 0.8 | 2.5 |
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300 mg |
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200 mg | 0.003 | 0.006 | 0.02 | 0.06 | 0.2 | 0.6 | 2 |
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100 mg | 0.003 | 0.005 | 0.016 | 0.05 | 0.16 | 0.5 | 1.6 |
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50 mg | 0.002 | 0.004 | 0.012 | 0.04 | 0.12 | 0.4 |
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30 mg |
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20 mg | 0.002 | 0.003 | 0.01 | 0.03 | 0.1 | 0.3 |
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10 mg | 0.002 | 0.003 | 0.008 | 0.025 | 0.08 | 0.25 |
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5 mg | 0.002 | 0.003 | 0.006 | 0.02 | 0.06 | 0.2 |
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3 mg |
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2 mg | 0.002 | 0.003 | 0.006 | 0.02 | 0.06 | 0.2 |
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1 mg | 0.002 | 0.003 | 0.006 |
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0.5 mg |
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* E0 is a theoretical tolerance that is 50% of OIML R 111 Class E1