Every pH meter gets a score from 0 to 100% built from six 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. Meters are grouped by form (pen testers, portable meters and benchtop meters) and use the same scale in every group.
| Factor | Measures | Weight |
|---|---|---|
| Accuracy | published pH accuracy | 30% |
| Calibration | most calibration points the meter accepts | 15% |
| Features | replaceable probe, ATC, waterproof rating and stored readings | 20% |
| Extra readings | conductivity (EC/TDS) and ORP with the included probe | 10% |
| Price | current price | 15% |
| Warranty | meter warranty length | 10% |
Where the numbers come from
Accuracy, range, calibration, features and warranty come from the maker’s spec page, datasheet or manual, or the maker’s own copy on a retail listing. Where the maker’s page and a listing disagree, the maker’s page is used. Prices are checked at Amazon and the maker’s own store, and the lowest price at a store the page links to is used.
The factors
Accuracy is the maker’s published pH accuracy, as a plus-or-minus figure, on a log scale, so each tenfold improvement counts the same. ±0.2 pH scores zero and ±0.005 pH full marks; ±0.1 pH scores about 19%, ±0.01 pH about 81%.
Calibration is the most calibration points the meter accepts. One point scores zero, two points 50%, three points 85%, four points 92% and five or more full marks. More points keep a meter accurate across the whole pH range, not just near pH 7.
Features is 30% for a replaceable probe or a cabled electrode, 25% for automatic temperature compensation, 25% for a waterproof housing and 20% for stored readings (on-board memory, USB output or a phone app). The waterproof share is full for IP67 or IP68, 60% for IP65, IP66, IP57 or a waterproof claim with no rating, and 30% for a lower rating such as IP54.
Extra readings counts measurements beyond pH and temperature that the meter takes with the probes in the box. One extra reading, conductivity (EC/TDS) or ORP, scores 70%, and both score full marks. Salinity adds 10%. A meter that reads ORP only with an electrode sold separately gets no credit for it.
Price is the current price on a log scale, so halving the price always counts the same: $600 scores zero and $60 full marks.
Warranty is the meter’s warranty: 1 year scores zero and 5 years full marks. Probe warranties, usually six months, are listed but not scored.
What isn’t scored
Resolution, measuring range, battery life, weight, probe warranty and release date are listed but not scored. Accuracy matters more than resolution: a meter that shows 0.01 pH steps is only as good as its stated accuracy.
Missing data
If a figure 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. There are two exceptions. A meter with no published pH accuracy scores zero for accuracy, because accuracy is the factor that most separates meters and an unstated figure can’t be trusted. A maker that doesn’t publish a warranty gets no warranty counted, so that factor 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.