Every air compressor gets a score from 0 to 100% built from five 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. Compressors are grouped by size, portable (tank under 10 gallons) and stationary (10 gallons and up), and some factors have their own scales for each group.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per CFM at 90 PSI | 30% |
| Airflow | SCFM at 90 PSI | 25% |
| Tank | tank size | 10% |
| Noise | stated sound level | 15% |
| Warranty | warranty length | 20% |
Where the numbers come from
Airflow, tank size, pressure, noise, motor, warranty and the rest come from the maker’s product page, spec sheet or manual, or the maker’s own copy on its Amazon listing. Prices are checked at Amazon and the maker’s own store, and the lowest is used. Battery compressors are priced as kits with a battery where one is sold.
The factors
Value is the current price divided by the airflow at 90 PSI, on a log scale for each group, so going from $100 to $50 per CFM counts as much as going from $200 to $100.
| Group | Scores 0 | Full marks |
|---|---|---|
| Portable | $240 per CFM | $50 per CFM |
| Stationary | $200 per CFM | $60 per CFM |
Airflow is the airflow at 90 PSI in SCFM: for portable compressors 1 CFM scores zero and 4 CFM full marks; for stationary compressors 3.5 CFM scores zero and 12 CFM full marks.
Tank is the tank size: for portable compressors 1 gallon scores zero and 6 gallons full marks; for stationary compressors 10 gallons scores zero and 60 gallons full marks.
Noise is the maker’s stated sound level: 85 dB(A) scores zero and 60 dB(A) full marks. Makers measure at different distances, which the product page notes where it’s given.
Warranty is the length of the consumer warranty on the compressor: 1 year scores zero and 5 years full marks.
What isn’t scored
Maximum pressure, airflow at 40 PSI, duty cycle, motor, weight and pump type are listed but not scored. Independent tests are listed where they exist, but there are too few to score.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as 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.