What size air compressor do I need? Size it by airflow, not horsepower or tank size alone: add up the CFM (cubic feet per minute) of the air tools you run at the same time, at the pressure they need, and add a safety margin. A garage with a brad nailer and a tire chuck needs very little air; a shop running sanders, grinders or a blaster all day needs a lot. Below: the air compressor size math, CFM for air tools, tank size, power, and when a two stage gas unit or rotary screw makes sense. Note: we sell shop and industrial compressors, not small portables.
How to work out air compressor size: CFM at PSI
Quincy Compressor’s sizing guide sets out the method most manufacturers use:
- List every air tool and its CFM rating. Quincy points out that air tools are rated by air volume (CFM at a given psig), not horsepower. If the CFM is not printed on the tool, check the manual or the maker’s website.
- Add the CFM of the tools that run at the same time.
- Add 25%. Quincy recommends this margin for error and future growth. Its example: tools totaling 500 CFM call for 625 CFM of compressor capacity.
- Use your highest pressure tool as the PSI baseline. The compressor must deliver your total CFM at that pressure, not just at a lower test pressure.
- Match the motor to your power supply, then weigh tank size, footprint and noise.
CFM for air tools: typical numbers
The figures below come from the Engineering ToolBox air consumption table, measured at roughly 90 psi. Two caveats from that source: the numbers are averages that vary a lot between manufacturers, and they assume the tool runs only about 25% of the time. The same page says full performance requires 4 times the volume, which matters for sanders and blasters that run nonstop.
| Air tool | Average CFM (about 90 psi, 25% load) |
|---|---|
| Brad nailer | 0.5 |
| Framing nailer | 2.5 |
| Tire inflation | 2 |
| Blow gun | 3 |
| 3/8 inch ratchet | 4 |
| 1/2 inch impact wrench | 4 to 5 |
| 1/4 inch die grinder | 4 to 6 |
| Orbital sander | 6 to 9 |
| Dual action sander | 11 to 13 |
| Production paint spray gun | 20 |
| Sand blaster | 6 to 400 |
Example: a 1/2 inch impact wrench (5 CFM) and a dual action sander (13 CFM) running together total 18 CFM. Add 25% and you are at 22.5 CFM. If the sander runs continuously, plan well above that, since the table assumes intermittent use.
Garage air compressor: what most homeowners need
If your list is a brad nailer, a framing nailer for weekend projects, tire inflation and a blow gun, your total is single digit CFM. Ferguson’s portable air compressor buying guide covers this end of the market well: hand carry units for inflating tires and light hobby work, pancake compressors as basic entry level units with small tanks, and hot dog compressors with tanks of roughly 1 to 7 gallons. Ferguson notes that bigger nailing jobs like flooring call for the largest hot dog tank or a twin stack unit.
We do not sell those small portables. If that list describes your garage, a home center portable is the right size, and a 10 HP screw compressor would be money and floor space you do not need. If you are fitting out the garage itself, our garage workbench height guide covers bench size and power outlets.
Rotary screw vs piston: when each makes sense
Two stage gas piston: off grid power and high pressure
The Wolverine 40 Gallon air compressor ($1,339) uses a 15 HP, 420cc gasoline engine with recoil or electric start, two stage compression, 175 psi max pressure and 24 CFM, with an ASME certified tank and low oil shutdown. It suits a ranch, job site or detached shop without heavy electrical service. It is a gas engine, so run it where the engine manual allows and never in a closed garage.
Rotary screw: continuous duty and multiple users
Our BBK Industrial screw compressors are rated at 125 PSI and are built for steady, all day air: production lines, auto shops with several bays, blasting and spraying. The listings describe a direct coupled motor and airend (no belts), an LCD controller with overload and temperature alarms, and acoustic insulation. The noise figure on the 10, 15 and 20 HP listings reads 62 plus or minus 2, with no unit stated, so ask us for details before you plan around it.
| Model | Air delivery | Power | Max current | Price |
|---|---|---|---|---|
| BBK 10 HP rotary screw | 34 CFM at 125 PSI | 460V 3 phase | 14.1 A | $3,531.99 |
| BBK 15 HP rotary screw | 56 CFM at 125 PSI | 208 to 230V 3 phase | 40.9 A | $4,627.99 |
| BBK 20 HP rotary screw | 74 CFM at 125 PSI | 208 to 230V 3 phase | 55.8 A | $5,174.99 |
| BBK 10 HP 4 in 1 with dryer and 39.6 gal ASME tank | 34 CFM at 125 PSI | 230V 3 phase | 28.5 A | $7,757.99 |
| BBK 20 HP 4 in 1 with dryer and 68.7 gal ASME tank | 74 CFM at 125 PSI | 230V 3 phase | 55.2 A | $9,657.99 |
See the full lineup on our BBK Industrial brand page.
Three phase power: talk to an electrician first
Quincy notes that commercial and residential buildings usually have single phase 115 volt power, while industrial facilities typically have three phase. Every BBK screw compressor above needs 208 to 230V or 460V three phase. Before you order, have a licensed electrician confirm what service you have, size the breaker and wire for the listed current, and handle the hookup to local code. If your building has no three phase service, that conversation comes before the compressor, or the gas unit may be the better fit.
Tank size and air dryers
Tank size
Quincy’s rule of thumb for smaller compressors is at least 5 gallons of tank per CFM. A tank covers brief peaks; it does not fix a compressor too small for steady demand. The 4 in 1 units include 39.6 and 68.7 gallon ASME tanks. If your demand comes in big surges, ask us whether an added receiver tank makes sense.
Refrigerated air dryers
Compressed air carries water. Our refrigerated dryers list a pressure dew point of 37.4 to 50°F, and the listings say they protect tools and equipment from corrosion and condensation. Pick a dryer rated at or above your compressor’s CFM:
- 63 CFM refrigerated air dryer ($1,826.99): matched to 10 and 15 HP compressors, 115V single phase, 3/4 inch NPT.
- 134 CFM refrigerated air dryer ($2,449.99): matched to 15, 20 and 30 HP compressors, 115V single phase, 1 inch NPT.
For floor protection under a heavy unit, see our garage floor tiles vs epoxy comparison, and for storing hoses and fittings, our NewAge garage cabinets review.
Frequently asked questions
What size air compressor do I need for air tools in a home garage?
Add the CFM of tools you run together and add 25%, per Quincy. For nailers, tire inflation and a blow gun, that is usually a small portable. Ferguson’s guide covers pancake, hot dog and twin stack units for that work.
How much CFM for air tools like impact wrenches and sanders?
Engineering ToolBox lists 4 to 5 CFM for a 1/2 inch impact wrench and 11 to 13 CFM for a dual action sander at about 90 psi, assuming 25% use. Continuous sanding needs more.
Is a rotary screw better than a piston compressor for a garage air compressor?
Only if the garage works like a shop: steady air for hours, several users, or blasting. Our screw units also need three phase power. For off grid heavy work, consider the two stage gas Wolverine.
Does a bigger tank mean a bigger air compressor size?
No. Tank size covers short peaks; CFM at your working PSI sets what the compressor can sustain. Quincy suggests at least 5 gallons per CFM on smaller units.
Still not sure which air compressor size fits your shop? Call us at 866-777-2590, Monday to Friday, 9AM to 6PM PST, with your tool list and power details. Shipping is free freight on orders of $999 or more, with a $200 flat rate below that. See our return and refund policy before you order.
