What Size Air Compressor Do You Need?
Choose an air compressor from the airflow your tools or process actually require at the correct working pressure, then check duty cycle, electrical supply, receiver size and air-treatment needs.
Quick Answer: Size the Compressor by Usable Airflow
The most important starting point is the amount of compressed air the application needs. Receiver litres, motor horsepower and kW are useful specifications, but none of them tells you on its own whether a compressor can keep up with the tools or machinery.
Use the air-consumption information supplied by the tool or machine manufacturer, identify what can operate at the same time and confirm the pressure at which that airflow is required.
The Five Things to Establish Before You Buy
Step 1: Calculate Simultaneous Air Demand
Start with the manufacturer's consumption data for every pneumatic tool, machine or process. The important figure is not the sum of every connected item, but the demand that can realistically occur at the same time.
For a Single Tool
Check its required airflow and pressure. Some tools quote average consumption while others specify continuous demand, so confirm exactly what the manufacturer's figure represents.
For Multiple Users
Add the demand of equipment that can run simultaneously and consider production peaks. A workshop with several people does not necessarily have every air tool operating continuously at once.
Tool Air Consumption: Use the Manufacturer's Figure
The previous version of this guide gave generic CFM ranges for impact wrenches, spray guns, plasma cutters, sanders and blasting equipment. Those figures can be useful as rough context, but they should not be used to size a compressor because actual consumption varies significantly between models and operating methods.
| Application | What to Check | Why It Matters |
|---|---|---|
| Impact wrench / ratchet | Manufacturer CFM at stated pressure and intended duty | Intermittent trigger use and sustained operation can produce very different air demand. |
| Spray gun | Gun air consumption, required pressure and spraying duration | Consistent airflow and correctly treated air can be important to finish quality. |
| DA / orbital sander | Continuous air consumption | Sanding can create sustained demand that quickly exposes an undersized compressor. |
| Plasma cutter | Exact machine airflow, pressure and air-quality specification | Requirements vary by machine and cutting conditions. |
| Sand / abrasive blasting | Nozzle size, pressure and continuous airflow from the equipment supplier | Blasting demand can become very high and must not be guessed from a generic CFM table. |
Step 2: Confirm the Working Pressure
Airflow only makes sense when considered at the pressure the process needs. Check the required pressure of the most demanding equipment and allow for genuine losses through pipework, hoses, dryers and filters.
- Use the pressure specified by the equipment manufacturer.
- Measure pressure at the point of use if the existing system suffers pressure loss.
- Investigate undersized pipework, blocked filters or excessive hose restriction rather than simply increasing compressor pressure.
- Check the compressor's delivered performance at the pressure you intend to run.
Step 3: Tank Size Helps — but It Does Not Create CFM
An air receiver stores compressed air and helps buffer short peaks in demand. It can also reduce rapid compressor cycling when correctly incorporated into the system. It does not increase the compressor pump's sustained airflow.
Short, Intermittent Demand
A receiver can be especially useful where tools operate in bursts because stored air can help support brief demand peaks while the compressor recovers.
Continuous Demand
If equipment continuously consumes more air than the compressor produces, a larger receiver only delays the eventual pressure drop. The compressor itself must be capable of meeting sustained demand.
Step 4: Match the Compressor to the Available Power Supply
Step 5: Piston, Fixed-Speed Screw or VSD?
Current Tanair Models From the Original Guide
The original page linked directly to a useful progression of Tanair compressors. Those product destinations are retained below, with the old broken 7.5 kW VSD URL corrected to the current live product page.
Air Treatment Can Change the Final System Size
If the application needs clean or dry compressed air, the dryer and filters must also be sized to handle the compressor's actual airflow under the operating conditions.
Refrigeration Dryers
Dryer selection depends on airflow as well as working pressure, compressed-air inlet temperature and ambient conditions. Do not simply match a dryer to compressor kW.
Filtration
Filters need adequate flow capacity and the correct grade for the required air quality. Undersized or contaminated elements can create unwanted pressure drop.
What Size Compressor for Common Workshop Jobs?
The safest answer is based on the exact equipment rather than a universal CFM value. Use the approach below when sizing for common applications.
Smoke Ventilation Is a Specialist Sizing Exercise
The original guide included semi-duplex, tandem and smoke-ventilation products. Those links are useful and are being preserved, but smoke ventilation should not be treated as another general workshop-CFM recommendation.
Smoke-control and other life-safety systems need to be specified against the system design, required pressure and stored-air volume, control philosophy, redundancy requirements and relevant project documentation.
Common Sizing Mistakes to Avoid
- Choosing from motor kW or HP without checking delivered airflow.
- Assuming a larger receiver compensates for inadequate continuous CFM.
- Using generic tool-consumption figures instead of the exact manufacturer's data.
- Ignoring the pressure required at the actual point of use.
- Buying a 230V compressor without checking current draw and starting requirements.
- Assuming VSD is automatically the best option regardless of the load profile.
- Forgetting dryer, filtration and pipework pressure losses.
- Oversizing excessively “for safety” without understanding actual future demand.
What Information Should You Send Us?
- Tool or machine make and model
- Manufacturer airflow requirement
- Required working pressure
- Number of simultaneous users
- Daily operating hours and duty pattern
- 110V, 230V or 400/415V supply available
- Whether dry or specially filtered air is required
- Any expected future increase in demand
Air Compressor Sizing FAQs
How do I calculate what size air compressor I need?
Add the airflow requirements of the tools or processes that can operate at the same time, using manufacturer data at the required pressure. Then consider duty cycle, leakage, future demand and sensible spare capacity before selecting the compressor.
Should I automatically add 20–30% to my CFM requirement?
No fixed percentage is correct for every system. Some spare capacity can be sensible, but the allowance should reflect measurement uncertainty, leakage, future expansion and the selected compressor's operating characteristics rather than an arbitrary universal figure.
Does a bigger tank mean more CFM?
No. The receiver stores air and can buffer short-term demand, but it does not increase the compressor pump's continuous airflow.
What CFM do I need for an impact wrench?
Use the airflow and pressure stated by the manufacturer of your exact impact wrench. Consumption varies by model and by how continuously it is used.
What size compressor do I need for spray painting?
Check the exact spray gun's airflow and pressure requirement, then make sure the compressor can sustain that demand for the required spraying time. Suitable drying and filtration may also be needed for finish quality.
Is 415V automatically better for continuous use?
No. Three-phase power makes larger motor sizes practical, but suitability for continuous or high-duty operation depends on the compressor design, airflow, duty rating and the application.
Should I choose piston or VSD?
Piston compressors can suit intermittent workshop demand. Screw compressors are commonly considered for more sustained industrial duty, while VSD can be particularly useful where airflow demand changes significantly. The correct option depends on the actual load profile.
Do I need a dryer and filters?
That depends on the process. Where moisture, particles or oil contamination would damage machinery or affect production quality, suitable air treatment should be selected and sized for the system.
Can you size a compressor for me?
Yes. Send us the tools or process, manufacturer airflow data, pressure, number of simultaneous users, duty cycle and available electrical supply. For larger systems, more detailed assessment or measurement may be appropriate.
Still Not Sure What Size Compressor You Need?
Send us the tools or machinery you need to run, their airflow and pressure requirements, how many will operate together and the electrical supply available. We can help narrow down the correct compressor and air-treatment setup.