What Is a Class 1 Load Cell? C1, C3 and NTEP Load Cell Classes Explained
Reviewed by MNM Scales technicians · Updated November 1, 2026 · Prices checked November 1, 2026
Short answer: A class 1 load cell is usually an OIML class C1 load cell: accuracy class C, rated for up to 1,000 load cell verification intervals. The number after the letter is the interval count in thousands, so a C3 cell is rated for 3,000 intervals and suits finer scale divisions. In the US, load cells for legal-for-trade scales carry an NTEP certificate that lists Class III or III L, the maximum number of divisions (nmax) and S or M for single or multiple-cell use. Less often, “Class 1” means a hazardous-location rating (Class I, Division 1) for areas with flammable gas or vapor.
Load cell data sheets are full of codes such as C1, C3, D1, III, IIIL, 5000S and 10M. Each one tells you how fine a scale the cell can support and where it may be used. MNM Scales has sold, installed and repaired load cells and scales for over 30 years from our shop in Cypress, Texas. This guide explains what a class 1 load cell is, how the OIML and NTEP classes compare, and how to match the class when you build or repair a scale.
What is a class 1 load cell?
Under the international load cell standard, OIML R 60, every load cell is ranked in one of four accuracy classes, A, B, C or D, and marked with the maximum number of load cell verification intervals (nLC) it supports. When the class and the interval count are combined into one symbol, the count is written in thousands. OIML R 60 gives the example C1: class C, 1,000 intervals. So when a buyer or a data sheet says “class 1 load cell”, it almost certainly means a C1 cell.
- C1: class C, up to 1,000 intervals.
- C2 and C3: class C, up to 2,000 and 3,000 intervals. C3 is the rating you will see on many platform and floor scale cells.
- C4 to C6: class C cells rated for 4,000 to 6,000 intervals, for higher-resolution scales.
- D1: class D, up to 1,000 intervals, the lowest OIML class.
A C1 cell is not worse at weighing than a C3 cell in every sense; it is approved for fewer divisions. Pick the class from the number of divisions your scale will show, then confirm capacity, output and mounting.
OIML load cell accuracy classes A, B, C and D
| OIML class | Interval range (nLC) | How it is written | What it means for you |
|---|---|---|---|
| A | 50,000 and up | A followed by the count | Highest class, for very high-resolution weighing |
| B | 5,000 to 100,000 | e.g. B10 | High-resolution weighing |
| C | 500 to 10,000 | C1, C2, C3 … C6 and up | The class most industrial and commercial scale cells carry |
| D | 100 to 1,000 | e.g. D1 | Lower-resolution weighing with few divisions |
What is a class D load cell? It is a load cell in the lowest OIML accuracy class, approved for 100 to 1,000 intervals. It fits scales with coarse divisions. For finer divisions, choose a class C cell with a higher number, such as C3.
C1 vs C3: matching the class to your scale
Count the divisions your scale will display: capacity divided by the division size. A 5,000 lb floor scale reading in 1 lb steps shows 5,000 divisions, while a 10,000 lb scale in 10 lb steps shows 1,000. The load cells, the indicator and the platform each have a maximum number of divisions, and the finished scale is limited to the lowest of them. NIST Handbook 44 states this for nmax: the installation is limited to the lowest nmax marked on the indicating element, weighing element or load cell.
- About 1,000 divisions or fewer: a C1 or D1 cell can cover it on paper, but many buyers still choose C3 for headroom.
- About 3,000 divisions: choose C3 or higher.
- 5,000 divisions or more: choose a cell rated for at least that many, such as an NTEP cell with nmax 5,000 or 10,000.
- Multi-cell scales: each cell also has a minimum verification interval (vmin) that has to be small enough for the scale division. Our scale tolerance calculator shows the Handbook 44 tolerances for a given division.
NTEP load cell classes: Class III, III L, nmax, S and M
In the US, scales used to buy or sell by weight follow NIST Handbook 44, and load cells for those scales carry an NTEP Certificate of Conformance. Handbook 44 uses Roman numerals for accuracy classes. Its Table 7a lists Class I for precision laboratory weighing and Class II for laboratory, precious metal and gem weighing. Load cells for commercial scales are usually certified for Class III (all commercial weighing not otherwise specified, such as retail, postal, animal and grain test scales) or Class III L (heavy-capacity uses such as livestock, crane and hopper scales). A Class I balance is a laboratory instrument, so “Class 1” on a load cell usually refers to the OIML C1 rating, not Handbook 44 Class I.
- nmax: the maximum number of divisions the cell is approved for, often written in thousands (5 = 5,000; 10 = 10,000).
- S or M: S means approved for single-cell scales and can also be used in multiple-cell scales; M means multiple-cell scales only.
- Example: the Zemic H8C single-ended beam is covered by NTEP Certificate of Conformance 12-028 for nmax 5,000 in Class III (single and multiple cell) and nmax 10,000 in Class III L (multiple cell). Its maker data sheet also lists OIML C3.
Read more in our guide to NTEP and legal-for-trade scales.
Load cells in stock and how they are rated
| Load cell | Type and capacity | Class or approval | Price |
|---|---|---|---|
| MNM Scales ZEMIC H8C-N5-2.5K-6YB | Single-ended shear beam, 2,500 lb | NTEP CC 12-028: Class III nmax 5,000 (S/M), Class III L nmax 10,000 (M) | $158 |
| MNM Scales GX-1-SSH-5K | Stainless steel washdown shear beam, 5,000 lb | NTEP; class and nmax are on the cell label and certificate | $121 |
| MNM Scales MS-1-100 lb tension load cell | S-type tension cell, 100 lb | NTEP | $129 |
| MNM Scales IDS-672-100klb-C3 | Pancake compression cell, 100,000 lb | C3 in the model name | $698 |
| MNM Scales JB-4SS-ST junction box | Stainless summing box for four cells | Accessory for multi-cell scales | $48.98 |
See every model in load cells, or compare shapes in our load cell types guide and sizing in the load cell buying guide.
Class I, Division 1: when “class 1” means a hazardous location
Hazardous-location ratings use the word Class too. Class I covers flammable gases or vapors, and Division 1 means they can be present in normal operation. A load cell or scale for those areas needs an intrinsically safe or other approved protection method, and a wired system needs a barrier that matches the maker’s control drawing. For battery-powered weighing in a Class I, Division 1 area, the A&D HW-100KCEP intrinsically safe bench scale ($2,099, 200 lb x 0.02 lb) is approved for Class I, Division 1, Groups C and D, T4. See our explosion proof scale guide for Class, Division and Zone markings.
How to read a load cell label or certificate
- Model and capacity: the rated capacity (Emax) in lb or kg.
- Accuracy class: an OIML symbol such as C3, or an NTEP class such as III or III L.
- Interval count: nLC or nmax, sometimes combined with the class (C3, 5000S, 10M).
- vmin: the smallest verification interval the cell supports.
- S or M: single-cell or multiple-cell approval on NTEP cells.
- Certificate number: the NTEP CC or OIML certificate, plus the serial number.
The Zemic H8C certificate, for example, describes a label on the cell that states the maker, model, serial number, rated capacity, vmin, class and CC number.
Replacing a load cell: match the class
- Match the capacity, output (mV/V), mounting and cable of the cell you are replacing.
- Match or exceed its class and nmax, and keep S or M approval suited to the scale.
- On a multi-cell scale, re-trim the junction box after the swap so every corner reads the same, then calibrate.
- Not sure the cell is bad? Follow our load cell test steps for zero balance, bridge resistance and insulation first.
- We repair scales and replace load cells in our Cypress shop, and on-site service is $295 + $2 per mile around Houston (see on-site calibration in Houston). Outside Houston, use mail-in calibration.
Using a scale in Texas: TDA does not require an NTEP certificate for every device, but the scale must meet NIST Handbook 44 and suit its use; some scales do need one, so we recommend NTEP models and can check yours. TDA explains this in Legal for Trade Scales in the State of Texas (PDF). See our TDA scale certification guide and floor scale buying guide.
Need a load cell that matches your scale? Send us the label photo or the model, capacity and division size, and we will quote a cell with the right class and nmax, plus a junction box, installation and calibration if you need them.
Frequently asked questions
What is a class 1 load cell?
It is usually an OIML class C1 load cell: accuracy class C, rated for up to 1,000 load cell verification intervals. A C3 cell is rated for 3,000 intervals.
What is a class D load cell?
A class D load cell is in the lowest OIML R 60 accuracy class, approved for 100 to 1,000 intervals. It suits scales with coarse divisions.
Is a C3 load cell better than a C1?
A C3 cell is approved for more divisions (3,000 instead of 1,000), so it supports a finer scale division. Choose the class from the number of divisions your scale will show.
Which load cells are used in legal-for-trade scales in the US?
Cells with an NTEP Certificate of Conformance for the class and nmax the scale needs, usually Class III or III L. The MNM Scales ZEMIC H8C ($158) is covered by NTEP CC 12-028 for Class III nmax 5,000 and Class III L nmax 10,000.
What do S and M mean on an NTEP load cell?
S means the cell is approved for single-cell scales and may also be used in multiple-cell scales. M means it is approved for multiple-cell scales only.
Is Class 1 the same as Class I, Division 1?
No. C1 is an accuracy rating. Class I, Division 1 is a hazardous-location rating for areas where flammable gas or vapor can be present in normal operation.