What Size Air Compressor Do I Need?
Choosing the right size air compressor depends on what you need to run, how often you use it, the pressure required and the amount of air your equipment consumes. This guide explains CFM, pressure, tank size and power so you can choose a compressor that suits your tools, workshop or business.
The Quick Answer
To choose the right air compressor, start with the tool or machine that needs the most air. Check its required CFM and working pressure, then choose a compressor that can comfortably exceed that demand.
As a simple rule, do not buy a compressor based only on tank size. The most important figure is usually air delivery, often shown as CFM or litres per minute.
What Does Air Compressor Size Actually Mean?
When people ask what size air compressor they need, they are usually talking about a mixture of tank size, motor power, pressure and air delivery. These are not the same thing.
CFMThe amount of air the compressor can deliver.
Bar / PSIThe pressure the compressor can produce.
Tank SizeHow much compressed air can be stored.
Motor PowerThe size of the motor, often shown in HP or kW.
CFM Is Usually the Most Important Figure
CFM stands for cubic feet per minute. It tells you how much air the compressor can supply. If your air tool uses more CFM than the compressor can produce, the compressor will struggle to keep up.
This can lead to pressure dropping, poor tool performance, longer recovery times and excessive compressor running.
Air Compressor Size Guide by Application
| Application | Typical Compressor Type | What to Consider |
|---|---|---|
| Inflating tyres and light DIY use | Small piston compressor | Low air demand, occasional use, compact size. |
| Staplers, nail guns and blow guns | Small to medium piston compressor | Check tool CFM and pressure requirements. |
| Impact wrenches and garage tools | Medium piston or screw compressor | Higher CFM needed, especially for regular use. |
| Spray painting | Compressor with steady air delivery | Requires consistent air flow and clean, dry air. |
| Workshop or small business use | Belt-driven piston or rotary screw compressor | Size based on number of users and air tools. |
| Industrial production | Rotary screw compressor | Continuous air demand, efficiency and duty cycle matter. |
How to Work Out What Size Compressor You Need
- List every air tool or machine you need to run.
- Find the CFM requirement for each item.
- Find the required pressure in bar or PSI.
- Identify which tool uses the most air.
- Consider whether multiple tools will run at the same time.
- Add a safety margin so the compressor is not working at its limit.
Do I Need a Piston or Screw Compressor?
Piston Compressors
Piston compressors are often suitable for smaller workshops, garages, mobile use and intermittent demand. They are a popular choice where air is needed occasionally rather than continuously.
Rotary Screw Compressors
Screw compressors are usually better for businesses with regular or continuous air demand. They are commonly used in workshops, production areas and industrial environments where reliability and efficiency are important.
Does Tank Size Matter?
Tank size does matter, but it should not be the only factor. A larger receiver gives you more stored air, which can help with short bursts of demand. However, if the compressor cannot produce enough CFM, a large tank will only delay the problem.
For regular air use, the compressor’s air delivery is more important than simply choosing the biggest tank.
What Pressure Do I Need?
Most air tools and equipment have a recommended working pressure. The compressor must be able to produce enough pressure for the equipment to operate correctly.
Always check the tool or machine specification rather than guessing. Some applications need higher pressure, while others need a high volume of air at a lower pressure.
Common Mistakes When Choosing an Air Compressor
- Choosing based only on tank size.
- Ignoring CFM and focusing only on HP.
- Buying too small and expecting the compressor to run continuously.
- Forgetting to allow for future expansion.
- Not allowing for multiple users or tools running at the same time.
- Forgetting about air quality, dryers and filtration.
Air Quality Also Matters
Choosing the right compressor size is only part of the decision. You may also need dryers, filters, drains and pipework depending on your application.
For example, spray painting, CNC machinery and production equipment may need cleaner, drier air than general workshop tools.
Air Compressor Sizing FAQ
What size air compressor do I need for air tools?
Check the CFM and pressure requirement of the air tool. Choose a compressor that can deliver more air than the tool requires, especially if the tool will be used regularly.
Is a bigger air compressor always better?
Not always. A compressor should be correctly sized for your demand. Oversizing can increase purchase cost and running cost, while undersizing can cause poor performance.
What size compressor do I need for a workshop?
This depends on the number of users, tools, machines and how often the air supply is needed. A small workshop may only need a piston compressor, while a busy commercial workshop may need a rotary screw compressor.
What is more important, HP or CFM?
CFM is usually more important because it shows the amount of usable air the compressor can deliver. HP alone does not tell you whether the compressor can keep up with your air demand.
Can Airmatic Compressors help me choose?
Yes. If you are unsure what size air compressor you need, contact Airmatic Compressors with details of your tools, equipment, usage and site requirements.
Need Help Choosing the Right Air Compressor?
If you are not sure what size air compressor you need, we can help. Tell us what tools or equipment you need to run, how often you use them and whether the compressor is for home, workshop or industrial use.