What Size Air Compressor Do I Need?

The most common question we get at the counter in Little Island is "what size compressor do I need?" The answer depends on the tools you want to run, not the size of the tank. Here is how to work it out.

1. Check how much air your tools use

Every air tool has an air consumption figure, usually in CFM (cubic feet per minute) or litres per minute. You will find it in the manual or on the box. Typical figures:

• Tyre inflating and blow guns: 1 to 3 CFM
• Nail and staple guns: 2 to 4 CFM
• 1/2" impact wrench: 4 to 6 CFM
• Spray guns: 4 to 12 CFM depending on the gun
• Dual action sanders and grinders: 8 to 12 CFM

2. Look at free air delivery, not displacement

Compressors are often advertised by displacement, which is the theoretical air the pump moves. Free air delivery (FAD) is what actually comes out, and it is usually 60 to 70% of the displacement figure. Always size on FAD.

3. Add a margin

Take the air use of your hungriest tool and add around 30%. That stops the compressor running flat out all the time, which wears it out early.

4. Pressure

Most air tools run at 6 to 6.3 bar (90 PSI). A compressor rated at 8 to 10 bar gives you enough headroom once you allow for the regulator and hose.

5. Tank size

The tank stores air, it does not make it. A bigger tank helps with short bursts like nailing or tyre work. For continuous tools like sanders and spray guns, the pump output matters far more.

Quick guide

• DIY, tyres, nailing: 24 to 50 litre direct drive
• Garage, impact wrenches, light spraying: 100 litre, 3HP
• Workshop, sanding, several users: 150 to 270 litre belt drive
• Production or all-day use: rotary screw compressor

Still not sure? Call us on 021 435 5424 or drop into our Little Island retail outlet (T45 NN60) and we will match a compressor to your tools. Browse our air compressors.