Every clamp meter gets a score from 0 to 100% built from eight factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Clamps are grouped into AC only, AC/DC, and 1,000 A and up, and use the same scale in every group.
| Factor | Measures | Weight |
|---|---|---|
| Current range | highest AC or DC current through the jaw | 15% |
| DC current | DC current through the jaw, or microamps through the leads | 15% |
| Safety rating | IEC 61010 measurement category (CAT) rating | 20% |
| Features | true RMS, inrush, LoZ, non-contact voltage, low-pass filter, temperature, DC microamps and phone app | 15% |
| Accuracy | basic AC current accuracy at 50/60 Hz | 10% |
| Jaw opening | jaw opening or largest conductor | 5% |
| Warranty | warranty length | 10% |
| Price | current price | 10% |
Where the numbers come from
Current ranges, accuracy, jaw opening, CAT ratings, features, weight and warranty come from the maker’s spec page, datasheet or manual, or the maker’s own copy on a retail listing. Where two of a maker’s own figures conflict, the value is left out rather than guessed. Prices are checked at the stores each page links to, and the lowest is used.
The factors
Current range is the highest AC or DC current the clamp reads through its jaw, on a log scale, so doubling the range always counts the same: 100 A scores zero and 2,000 A full marks. Flexible probes sold as accessories are listed but not scored.
DC current is full marks for a clamp that reads DC current through the jaw, 25% for one that reads only DC microamps through the test leads (the flame-sensor check on furnaces), and zero for none.
Safety rating is the IEC 61010 measurement category. CAT IV 600 V scores full marks and CAT IV 300 V scores 75%. CAT III 1000 V scores 80%, CAT III 600 V 55% and CAT III 300 V 25%. A meter rated only CAT II scores 10%. A meter with several ratings gets the best of them.
Features is 25% for true RMS, 15% for inrush, 15% for LoZ (low impedance) voltage, 10% for non-contact voltage detection, 10% for a low-pass or VFD filter, 10% for a temperature input, 10% for a phone app, and 5% for DC microamps.
Accuracy is the basic AC current accuracy at 50/60 Hz, as a percentage of reading: 3% scores zero and 1.5% full marks.
Jaw opening is the jaw opening or largest conductor the maker states: 20 mm scores zero and 50 mm full marks.
Warranty is the maker’s warranty: 1 year scores zero and 3 years full marks.
Price is the current price on a log scale: $500 scores zero and $50 full marks.
What isn’t scored
Voltage range, resistance, capacitance and frequency ranges, display count, weight, work lights, flexible probe ranges and release date are listed where published but not scored.
Missing data
If accuracy or jaw opening isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. Features score neutral only when none of them is published; a feature the maker doesn’t mention otherwise counts as absent. Two factors are exceptions. A meter with no published CAT rating scores zero on safety, because the safety rating is what most separates one clamp from another and an unrated meter can’t be assumed safe. A maker that doesn’t publish a warranty gets no warranty counted, so that factor also scores zero, the same as a one-year warranty. Both are marked estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.