AIR SYSTEM SIZING TOOL
Air Compressor CFM Calculator
Match the compressor’s CFM at 90 PSI to the highest simultaneous tool load, then add 25 to 50 percent. CFM is the flow of air, PSI is the pressure, and most air tools are rated at 90 PSI. A compressor that cannot hold 90 PSI while the tool runs will make the tool feel weak, no matter how large the tank.
KEY TAKEAWAYS
How to Size an Air Compressor for Air Tools
Four rules decide whether the compressor keeps up with the tools. Read them before you compare CFM numbers on a spec sheet.
CFM and PSI
Are Two Numbers
CFM is the flow of air, PSI is the pressure. Most air tools are rated at 90 PSI — a compressor that cannot hold that pressure under load will make the tool feel weak.
Size to the Highest
Simultaneous Load
Add the CFM of every tool that runs at the same time. Then add 25 to 50 percent of margin — the common rule of thumb is 1.5× the total.
Continuous vs
Intermittent Tools
Continuous tools — die grinders, sanders — need roughly twice their rated CFM. Intermittent tools — impact wrenches — can share a smaller pump.
Tank Buffers,
It Does Not Replace
Tank size buffers demand and reduces cycling. It does not replace CFM output — a large tank on a small pump still runs out under continuous load.
Three Numbers
to Read First
CFM, PSI and tank size — those are the three numbers you actually need from a compressor spec. Any claim without them is incomplete.
AIR COMPRESSOR CFM CALCULATOR
Size a Compressor for Your Air Tools
Add the CFM of every tool that runs at the same time at 90 PSI, then apply the safety factor. The result is the minimum compressor CFM that will keep up with your tools under load.
TOOL LOAD
Simultaneous Tools
CFM
Example: 1/2″ impact wrench ≈ 5 CFM
CFM
Example: die grinder ≈ 6 CFM
CFM
Leave at 0 if not used
CFM
Leave at 0 if not used
A tool that runs nonstop — die grinder, sander — needs about twice its rated CFM. Enter the doubled figure above for continuous tools. Intermittent tools (impact wrench, nailer) can use the rated value.
REQUIRED COMPRESSOR
Live Result
Minimum Compressor CFM at 90 PSI
16.5
CFM
Total tool load 11.0 CFM × 1.5 safety factor.
Total Tool Load
11.0 CFM
Safety Factor
1.5×
Active Tools
2 tools
Recommended Tank
20–30 gal
SIZING METHOD
Required CFM = Σ Tool CFM × Factor
5.0 + 6.0 = 11.0 × 1.5 = 16.5 CFM
Σ
11.0 CFM
Tool load
×
1.5
Safety factor
=
16.5 CFM
Required
Tank size does not replace CFM.
A large tank buffers demand and reduces cycling, but a small pump still runs out under continuous load. CFM and PSI decide whether the tool feels strong — the tank only smooths the supply.
AIR TOOL REFERENCE
Typical CFM at 90 PSI
Reference values only. Actual CFM depends on the specific tool model, air pressure setting and duty cycle. Always confirm against the manufacturer’s rating on the tool label.
Impact Wrench 1/2″
4–5
Impact Wrench 3/4″
6–8
Die Grinder
5–7
Air Ratchet
3–5
DA Sander
10–15
HVLP Spray Gun
10–14
COMPRESSOR SIZING
How to Size a Compressor for Your Tools
RULE OF THUMB
Σ CFM × 1.5
Two decisions drive the number: which tools run at the same time, and whether they run continuously. Add only the tools that run simultaneously, then apply a duty-cycle margin.
Simultaneous Load
Sum CFM
Only tools running together
Duty Margin
× 1.5
Covers both duty types
Horsepower Proxy
1 HP
Per 4 CFM at 90 PSI
Working Pressure
90 PSI
Most air tools
SIZING METHOD
Add Tools, Then Multiply
Step 01 · Add
Simultaneous tools only
Step 02 · One at a time
Size to the highest single tool
Step 03 · Continuous
Roughly 2× rated CFM
Step 04 · Total
Sum × 1.5
WORKED EXAMPLE
Impact + Grinder
5 + 11 CFM
16
CFM
×1.5
Required
× 1.5
24
CFM
1 HP
per 4 CFM at 90 PSI —
confirm CFM, not horsepower
!
Horsepower is a rough proxy, not a substitute. Plan on roughly 1 HP for every 4 CFM of output at 90 PSI. A compressor that must deliver 16 CFM wants about 4 HP, but always confirm the CFM rating on the spec sheet rather than buying by horsepower.
THREE NUMBERS
CFM vs PSI vs Tank Size
Three numbers appear on every compressor spec, and they do three different jobs. Confusing them is the most common mistake when sizing a compressor.
FLOW
CFM — Cubic Feet per Minute
The volume of air the pump delivers. This is the number that runs the tool. SCFM is standard CFM, corrected to fixed temperature and pressure so two compressors can be compared fairly.
PRESSURE
PSI — Pounds per Square Inch
The pressure the compressor must hold while the tool draws air. Most air tools run at 90 PSI. A compressor that delivers plenty of CFM at 40 PSI but drops at 90 PSI will not run an impact wrench.
BUFFER ONLY
Tank Size — Stores Air, Does Not Add CFM
Larger tank
Fewer pump cycles
Steadier pressure
At the start of a burst
Once the tank empties
Pump output is the ceiling
Rule
Tank does not replace CFM
A large tank on a small pump still runs out under
continuous load.
Tank size buffers demand and reduces cycling, but the pump’s CFM output is the ceiling. The right compressor is the one that keeps up in real time, not the one with the largest tank.
AIR TOOL REFERENCE
Typical CFM at 90 PSI
REFERENCE
Ranges Vary by SKU
Typical air consumption at 90 PSI. Ranges vary by make and duty cycle, so treat these as reference values and confirm the rating on the specific SKU before finalizing a compressor.
| Air Tool | Typical CFM at 90 PSI | Duty |
|---|---|---|
| Brad Nailer | 0.3 | Intermittent |
| Framing Nailer | 2.2 | Intermittent |
| Tire Inflator | 2 to 3 | Intermittent |
| Blow Gun | 2 to 3 | Intermittent |
| Air Ratchet (3/8 in) | 3 to 5 | Intermittent |
| Air Drill (3/8 in) | 3 to 6 | Intermittent |
| Impact Wrench (1/2 in) | 4 to 6 | Intermittent |
| Die Grinder (1/4 in) | 4 to 7 | Continuous |
| Cut-Off Tool | 4 to 10 | Continuous |
| Angle Grinder (7 in) | 5 to 8 | Continuous |
| Orbital Sander | 6 to 12 | Continuous |
| Impact Wrench (3/4 in) | 7 to 10 | Intermittent |
| Impact Wrench (1 in) | 10 to 12 | Intermittent |
| HVLP Spray Gun | 12 to 15 | Continuous |
!
“Average” ratings assume a duty cycle around 25%. Under continuous load a tool draws more — which is why continuous tools (die grinders, sanders, spray guns) carry the larger multiplier in the sizing step. Intermittent tools pause between bursts and a smaller pump catches up.
Frequently Asked Questions (FAQs)
Find answers to common questions about our hand tools, their care, and usage. If you need additional information, our customer support team is ready to assist you.
What Size Air Compressor Do I Need for Air Tools?
List the tools that run at the same time, add their CFM at 90 PSI, and multiply by 1.5. A single 1/2 in impact wrench needs about 8 CFM; an impact wrench plus a die grinder needs about 16 CFM.
How Many CFM Does an Impact Wrench Need?
A 1/2 in impact wrench draws about 4 to 6 CFM at 90 PSI; a 3/4 in draws 7 to 10 CFM; a 1 in draws 10 to 12 CFM. Size for at least 1.5 times the tool’s CFM.
What Is the Difference Between CFM and PSI?
CFM is flow, the volume of air delivered per minute; PSI is pressure, the force of that air. A tool needs both: enough PSI to operate (usually 90) and enough CFM to sustain it under load.
Does Tank Size Matter for Air Tools?
Yes, but it is not a substitute for CFM. A bigger tank buffers demand and reduces pump cycling, which helps intermittent tools. For a continuous tool, the pump’s CFM output is what matters.
How Many CFM Does a Die Grinder Use?
About 4 to 7 CFM at 90 PSI. Because it runs continuously, size the compressor for roughly double the rated figure, around 8 to 14 CFM.
Can I Run an Impact Wrench on a 6 Gallon Compressor?
Usually not for sustained work. A 6 gallon tank with a small pump (often 2 to 3 CFM) cannot keep up with a 1/2 in impact wrench’s demand; it works in short bursts, then the tool slows as pressure drops.