Scale Tolerance Calculator (NIST Handbook 44)

Reviewed by MNM Scales technicians · Updated October 27, 2026

This free calculator gives the Handbook 44 tolerance for any scale marked Class I, II, III, IIII or III L. Enter the accuracy class, the verification scale interval e, the units and the test load. It returns the load in e, the Table 6 band, and the maintenance and acceptance tolerances in e and in your units, with the allowed reading range. MNM Scales has calibrated and repaired scales for over 30 years, and our TDA-registered technicians use these same tables every day on bench, floor, crane and counting scales and on laboratory balances. The values come from the current edition, NIST Handbook 44 (2026), Section 2.20 Scales.

How the calculator works

• Step 1, find e. The verification scale interval is marked on the scale. On Class III, III L and IIII scales e equals the display division d (Section 2.20, S.1.2.2.2). Class I and II balances can show a finer d than e, so always use e.
• Step 2, convert the test load to e. Test load / e. A 30 lb weight on a 0.02 lb scale is 30 / 0.02 = 1,500 e.
• Step 3, read Table 6. Find the band for that number of e in your class row. That is the maintenance tolerance in e (T.N.3.1).
• Step 4, halve it for acceptance. Acceptance tolerance = one-half the maintenance tolerance (T.N.3.2).
• Step 5, convert back to units. Multiply by e. The tolerance applies plus and minus, from zero with no load, or from the tare zero when tare is in use (T.N.2.1).

NIST Handbook 44 Table 6: maintenance tolerances

NIST Handbook 44 (2026), Section 2.20, Table 6. Maintenance Tolerances (all values in e). Acceptance tolerance = one-half of these values.

Class	1 e	2 e	3 e	5 e
I	0 to 50,000 e	50,001 to 200,000 e	200,001 e and up	–
II	0 to 5,000 e	5,001 to 20,000 e	20,001 e and up	–
III	0 to 500 e	501 to 2,000 e	2,001 to 4,000 e	4,001 e and up
IIII	0 to 50 e	51 to 200 e	201 to 400 e	401 e and up
III L	0 to 500 e	501 to 1,000 e	Add 1 e for each additional 500 e or fraction thereof

For a load between two listed values, the tolerance for the lower value applies (General Code G-T.4). For multi-interval and multiple range scales, use e of the range in use (T.N.2.4). Crane and hopper scales (other than grain hopper scales) use the Class III L values, and their tolerance may not be less than 1 e or 0.1 % of scale capacity, whichever is less (T.N.3.4); tick the crane box in the calculator to apply it.

Worked example: Class III bench scale, 60 lb x 0.02 lb

A grocery or seafood counter scale is marked Class III, Max 60 lb, e = 0.02 lb. The technician places a certified 30 lb test weight on it.

• Load in e: 30 lb / 0.02 lb = 1,500 e.
• Table 6, Class III: 1,500 e is in the 501 to 2,000 e band, so the maintenance tolerance is 2 e = ±0.04 lb. In use, the scale passes if it reads 29.96 to 30.04 lb.
• Acceptance tolerance: half of 2 e = 1 e = ±0.02 lb. A new scale, or one just repaired or placed in service, must read 29.98 to 30.02 lb.
• At full capacity (60 lb = 3,000 e) the band is 2,001 to 4,000 e: maintenance 3 e = ±0.06 lb, acceptance 1.5 e = ±0.03 lb. Because the display moves in 0.02 lb steps, a new scale reading 60.02 lb passes and one reading 60.04 lb needs adjusting.

More examples

Scale	Test load	Load in e	Maintenance	Acceptance
Class II balance, e = 0.01 g	200 g	20,000 e	±2 e = ±0.02 g	±1 e = ±0.01 g
Class III bench scale, 60 lb x 0.02 lb	30 lb	1,500 e	±2 e = ±0.04 lb	±1 e = ±0.02 lb
Class III bench scale, 60 lb x 0.02 lb	60 lb	3,000 e	±3 e = ±0.06 lb	±1.5 e = ±0.03 lb
Class III floor scale, 5,000 lb x 1 lb	1,000 lb	1,000 e	±2 e = ±2 lb	±1 e = ±1 lb
Class III L crane scale, 2,000 lb x 1 lb	2,000 lb	2,000 e	±4 e = ±4 lb	±2 e = ±2 lb

Which accuracy class is my scale?

The class is on the scale’s identification plate and on its NTEP Certificate of Conformance. Handbook 44 Table 7a lists the typical class for each application: Class I for precision laboratory weighing; Class II for laboratory weighing, precious metals and gem weighing; Class III for most other commercial weighing, including retail precious metals, postal and shipping, animal and counter scales; and Class III L for large-capacity scales such as livestock, crane and hopper scales. A higher class than the typical one may always be used. Pawn shops and jewelers buying gold by weight, for example, use Class II balances. See our guide to NTEP and legal-for-trade scales or browse NTEP legal-for-trade scales.

Why tolerance matters for Texas legal-for-trade scales

If you sell, buy or charge by weight in Texas, your scale is a commercial device. The Texas Department of Agriculture (TDA) adopts NIST Handbook 44 by reference, and its legal-for-trade guidance says Handbook 44 sets the minimum standards TDA inspectors use to decide the outcome of a weights and measures inspection, including accuracy. A scale inside the maintenance tolerance passes the accuracy test; a new or just-repaired scale must meet the tighter acceptance tolerance.

Commercial scales in Texas are registered with TDA by the business on the RWM-700 device registration application, and installation, calibration and repair are done by a TDA-licensed service company with registered technicians, who file the RWM-780 service report when required. Our customers include grocery stores, seafood businesses, pawn shops, pharmacies, food manufacturers and distributors, and steel, fastener and chemical plants around Houston. For the full Texas picture, see TDA scale requirements in Texas. Not sure your scale has to be legal for trade at all? Try our Texas legal-for-trade scale checker.

Scale calibration from MNM Scales

• TDA-registered technicians for every scale class, with legal-for-trade calibration in Texas, placing scales in service and RWM-780 reports.
• On-site service across the Houston area: $295 + $2/mile round trip per visit, with calibration charged per scale. Our technicians bring their own certified test weights for floor and crane scale calibration. Dallas, Austin and San Antonio on request.
• Mail-in calibration for Texas and nationwide (in states that accept TDA calibration), including scales bought elsewhere; usually 1 to 3 business days after we receive the scale.
• Certificates: in-house calibration with NIST-tested weights, or NIST calibration with a NIST-traceable certificate. See what scale calibration costs.
• Shop visits by appointment at our Cypress, TX shop, and scale rentals of all types while yours is in service.

Book calibration, call (832) 290-3120 or send us your scale model.

Frequently asked questions

What is the difference between acceptance and maintenance tolerance?

Maintenance tolerances apply to a scale in normal use. Acceptance tolerances apply to a scale put into commercial use for the first time, one officially tested within 30 days of being placed in service or of corrective service or major reconditioning, and to type evaluation. For scales marked with an accuracy class, the acceptance tolerance is one-half the maintenance tolerance (NIST Handbook 44, G-T.1, G-T.2 and Section 2.20 T.N.3.2).

Is the tolerance based on d or e?

On e, the verification scale interval (T.N.1.3). On Class III, III L and IIII scales e must equal d, the displayed division. Class I and II balances may show a smaller d than e, for example d = 0.001 g with e = 0.01 g, so use the e marked on the balance.

How do I find my scale’s accuracy class and e?

Both are marked on the scale’s identification plate or label, for example “Class III, Max 60 lb, e = 0.02 lb”, and they also appear on the scale’s NTEP Certificate of Conformance.

Which tolerance applies to a test load between two table values?

The tolerance for the lower listed load (General Code G-T.4). For example, a Class III test load of 500.5 e uses the 0 to 500 e band, so the maintenance tolerance is 1 e.

How does the Class III L rule work above 1,000 e?

Table 6 gives Class III L 1 e up to 500 e and 2 e from 501 to 1,000 e, then adds 1 e for each additional 500 e or fraction of 500 e. So 1,001 to 1,500 e is 3 e, 1,501 to 2,000 e is 4 e, and so on.

Does Texas use NIST Handbook 44?

Yes. The Texas Department of Agriculture adopts NIST Handbook 44 by reference in its weights and measures rules (4 TAC Chapter 12), and TDA says Handbook 44 sets the minimum standards its inspectors use for legal-for-trade scales.

What should I do if my scale reads outside the tolerance?

Have it adjusted or repaired and then calibrated with certified test weights. In Texas, commercial scale calibration and repair is done by a TDA-licensed service company with registered technicians, who file the RWM-780 service report with TDA when it is required.

Disclaimer: this calculator is an aid for planning and checking tests. The official text of NIST Handbook 44, Section 2.20 Scales, as adopted by your state, governs. It covers the general Table 6 tolerances; special rules for certain systems (for example in-motion, monorail and materials tests, T.N.3.6 to T.N.3.9) are not included. Source: NIST Handbook 44, 2026 edition, doi.org/10.6028/NIST.HB.44-2026.