ASTM Class 1 Calibration Weights

All sales on calibration weights are FINAL. Once you place an order for a calibration weight, it may not be canceled. Please be sure you have the correct item before you place your order. Calibration weights are custom manufactured and are certified on the date they are created. In addition, simply touching these weights with your hand can change the tolerance due to the oil in your skin. We will not accept any exchanges or refunds on calibration weights. No exceptions.

Which calibration weight should you choose?
A balance should be calibrated using a weight with a class tolerance factor greater than the readability of the balance.  For example if your balance has a readability of 1mg it should be calibrated with a weight having a known tolerance of .1mg or less.

What are the class differences?

OIML E2 provides the greatest precision we offer.  They are ideal for use as reference standards to calibrate other weights or for calibrating high-resolution analytical balances. The OIML E2 tolerance is approximately two times the precision of ANSI/ASTM Class 1.

ANSI/ASTM Class 1 can be used as reference standard in calibrating other weights and appropriate for calibrating high-precision analytical balances (from 0.01mg to 0.1mg).

ANSI/ASTM Class 2 Appropriate for calibrating high-precision toploading balances with readabilities ranging from 0.001g to 0.01g.

ANSI/ASTM Class 3 Appropriate for calibrating balances with moderate precision, ranging from 0.01g to 0.1g.

ANSI/ASTM Class 4 Appropriate for student use and semi-analytical weighing.

NIST Class F Used to test commercial weighing devices by state and local weights and measures officials, device installers and service technicians. Class F weights may be used to test most accuracy class III scales, all scales of class III L or IIII, and scales not marked with a class designation.

Metric Weight Tolerances - all tolerances stated in milligram (mg)
	(ASTM) American Society of Testing & Measurement
Denomi- nation Metric	Class 1 mg	Class 2 mg	Class 3 mg	Class 4 mg	Class 5 mg	Class 6 mg	Class 7 mg
5 kg	12	25	50	100	250	500	1400
3 kg	7.5	15	30	60	150	300	1000
2 kg	5.0	10	20	40	100	200	750
1 kg	2.5	5.0	10	20	50	100	470
500 g	1.2	2.5	5.0	10	30	50	300
300 g	0.75	1.5	3.0	6.0	20	30	210
200 g	0.50	1.0	2.0	4.0	15	20	160
100 g	0.25	0.50	1.0	2.0	9	10	100
50 g	0.12	0.25	0.60	1.2	5.6	7
30 g	0.074	0.15	0.45	0.90	4.0	5	44
20 g	0.074	0.10	0.35	0.70	3.0	3	33
10 g	0.050	0.074	0.25	0.50	2.0	2	21
5 g	0.034	0.054	0.18	0.36	1.3	2	13
3g	0.034	0.054	0.15	0.30	0.95	2	9.4
2 g	0.034	0.054	0.13	0.26	0.75	2	7.0
1 g	0.034	0.054	0.10	0.20	0.50	2	4.5
500 mg	0.010	0.025	0.080	0.16	0.38	1	3.0
200 mg	0.010	0.025	0.060	0.12	0.26	1	1.8
100 mg	0.010	0.025	0.050	0.10	0.20	1	1.2
50 mg	0.010	0.014	0.042	0.085	0.16	0.5	0.88
20 mg	0.010	0.014	0.035	0.070	0.12	0.5	0.56
10 mg	0.010	0.014	0.030	0.060	0.10	0.5	0.4
5 mg	0.010	0.014	0.028	0.055	0.080	0.2
2 mg	0.010	0.014	0.025	0.050	0.060	0.2
1 mg	0.010	0.014	0.025	0.050	0.050	0.1

(OIML) International Organization of Legal Metrology Recommendation R111
E1 mg	E2 mg	F1 mg	F2 mg	M1 mg	M2 mg	M3 mg
2.5	7.5	25	75	250	750	2500
1.0	3.0	10	30	100	300	1000
0.5	1.5	5	15	50	150	500
0.25	0.75	2.5	7.5	25	75	250
0.1	0.30	1.0	3.0	10	30	100
0.05	0.15	0.5	1.5	5	15	50
0.030	0.10	0.30	1.0	3.0	10	30
0.025	0.080	0.25	0.8	2.5	8	25
0.020	0.060	0.20	0.6	2	6	20
0.015	0.050	0.15	0.5	1.5	5	15
0.012	0.040	0.12	0.4	1.2	4	12
0.010	0.030	0.10	0.3	1.0	3	10
0.008	0.025	0.08	0.25	0.80	2.5
0.006	0.020	0.06	0.20	0.6	2
0.005	0.015	0.05	0.15	0.5	1.5
0.004	0.012	0.04	0.12	0.4
0.003	0.010	0.03	0.10	0.30
0.002	0.008	0.025	0.08	0.25
0.002	0.006	0.020	0.06	0.20
0.002	0.006	0.020	0.06	0.20
0.002	0.006	0.020	0.06	0.20