Air Compressor Buying Guide

At SGS, there is a huge range of direct-drive and belt-drive air compressors. We understand that it can seem daunting to try to pair your air tools with a specific air compressor. Especially as the range of choices available is so broad. Air compressors can be used for all manner of work on vehicles and at home. For example, touching up the paintwork, wrenching off wheel nuts, cutting metalwork, etc. How do you know which one you should use? The best air compressor isn't always the right air compressor for the job. We've put together a simple user guide and check list to help you narrow the field and decide which compressor is worth your investment.

Quick Start Guide

1. What will you be using the compressor for?

Having an understanding of what you will be using your air compressor for is the most important factor when looking to buy a compressor. All compressors come with specific warranties to cover infrequent use for DIY jobs or frequent use. Make sure you choose the right compressor for your application. If you have a specific job in mind, then check out our compressor kits, which have everything you need to get started.

2. The CFM requirement

The CFM requirement is the single biggest consideration when buying a compressor. Knowing what CFM your air compressor needs to produce in order to power all of your air tools. Find the SCFM requirement of your tool in its manual or technical specification.

Example: If you want to run a spray gun (6 SCFM):

6 SCFM x 1.2 = at least a 7.2 CFM compressor

3. Choosing a tank size

With tank sizes ranging from 6 litres to 500 litres+, choosing the perfect capacity air tank or receiver will seriously affect the performance of your compressor. To find the minimum tank size of the compressor, you need to multiply your tool’s required SCFM by 6.

For example, If you run an impact wrench (8 SCFM):

8 SCFM x 6 = at least a 48-litre compressor tank

4. Oil-less or oil-compressor

Oil-less compressors are low-maintenance and free from contaminants. A standard oiled compressor will generally produce a larger output and run quieter.

Direct Drive or Belt Drive?

We split our range of compressors into two specific ranges: direct drive and belt drive, each with its own specific warranty tailored for its intended use. If you’re a DIY user, hobbyist, or occasional user of an air compressor, we’d suggest one of these SGS compressors. Competitively priced and complete with a 2-year domestic warranty, SGS compressors are very portable and perfect for occasional nailing, stapling, drilling, tyre inflation, air brush painting, or blow cleaning. Designed with the DIY user in mind, they're ideal for working in the garage at the end of the week or on a track day.

If you’re going to be using a compressor more consistently or even every day, we stock a wide range of commercial and workshop compressors. SGS and ABAC belt-drive compressors are designed for a variety of applications. Our professional portable compressors are perfect for service engineers, upholsterers, and many other mobile users, while our stationary compressors are ideal for workshops and industrial settings.

Direct-drive compressors

This range of direct-drive compressors is designed for home use, hobbyists, and semi-professional applications. Fantastic value for money and perfect for anyone wanting to occasionally use a compressor. With a two-year domestic warranty and free delivery on orders over £100, these compressors are among the best in the consumer market.

Belt-Drive Compressors

Perfect for workshop and industrial setups, these compressors come with anti-vibration feet for minimal noise pollution and a large receiver (an air tank) for heavy-duty usage. Whether portable or stationary—electric, petrol, or diesel-powered—our industrial air compressors allow you to have the choice and control to decide exactly what your business needs are.

Understanding the Required CFM

One of the most important considerations when purchasing a new air compressor is the amount of air flow the compressor can deliver. Air tools have certain requirements to run at optimum capacity. More important is the required SCFM, or standard cubic foot per minute.

All air tools will have a required SCFM, but in general, smaller air tools require between 0 and 5 SCFM. While larger tools can need 10 or more SCFM, CFM stands for cubic feet per minute and is the volume of air the compressor can pump out per minute.

The first thing you need to work out is how much air you will need to power your tool. To work this out, we need to know how much air flow the compressor produces and how much your tool requires to run. Most air tools will have specific requirements for air volume and pressure. Your compressor must meet these requirements for the tool to function the best it can.

Working out your CFM requirement

1. Find the required air flow (SCFM) of your air tools. This information will be in your tool user guide or manufacturer's website.
2. If you’re going to be running multiple tools, you’ll need to add together the individual SCFMs of each tool. Most DIY compressors are designed to run only one tool at a time. You can successfully run several tools simultaneously on larger, more commercial compressors.
3. To find the minimum required CFM of the compressor you need, multiply your tool’s required SCFM by 1.2.

Example: If you want to run a spray gun (6 SCFM),

6 SCFM x 1.2 = at least a 7.2 CFM compressor

This is only a rough guide. Larger compressors with higher CFM and bigger tanks will always give you better-performing tools. You may prefer buying the largest compressor within your budget.

Typical SCFM requirements

These are some typical values for various air tools. You should always check the exact requirements of your tool by consulting its user guide.

CFM vs. FAD

CFM (FAD) is generally third less than CFM (displacement); if your air compressor is advertised as 10 CFM (displacement), the Free Air Delivery (FAD) is probably around 6.6 CFM.

FAD is "free air delivery" and is the volume of air actually discharged. Compressors are always listed with the theoretical displacement, not the actual amount of air delivered. FAD is far more useful than CFM, as you can see the actual “power” a compressor has available for tools, etc.

TOP TIP: Air flow is lost through air hoses, hose fittings, filters, lubricators, and especially through quick-connect couplings. If you do plan to run your air tool some distance away from the actual compressor or with any of these peripherals, you will need to consider this pressure drop when choosing your compressor. The more CFM your compressor produces, the better your tool will run, even with longer hoses and more fittings.

TOP TIP: Never use extension leads with air compressors! The voltage drop from an extension cable can damage the air compressor motor. Instead, use a longer air hose.

Working Pressure

The pressure generated inside the tank of an air compressor is measured in bars and pounds per square inch, or PSI. Most compressors have a working pressure of 8 bar or 115 PSI, which is more than sufficient for DIY and hobby air tools (normally around 90 PSI).

Some of the more powerful air compressors we sell in our commercial range have higher working pressures (145 PSI+). Again, you can always check to see whatworking pressure is required for your air tool by looking at the user manual or contacting the manufacturer.

Working out your required tank size

As a rule, the larger the air tank your compressor has, the better and longer your tool will run at a more consistent CFM. Because a larger air tank will be depleted less often than a smaller tank, it’s worth investing in a large enough tank to complete the job you have in mind. For example, even though a spray gun will work with a small 6-litre compressor, it will only work in very short bursts. 6 litres would be plenty for spraying the body of a guitar; however, if you want to paint a whole car or van, you’d probably want at least a 100-litre air compressor.

To find the minimum tank size of the compressor, you need to multiply your tool’s required SCFM by 6.

For example, if you run an impact wrench (8 SCFM),

8 SCFM x 6 = at least a 48-litre compressor tank

Again, this is a rough guide, and the larger tank your compressor has, the better the performance of your tool. Below is a table of our range of compressors to help you choose the right one for your applications.

Electric, Petrol, or Diesel

With a conventional electrical air compressor, you’ll always be limited in where you can set up and get on with your project, as you need to be near a mains power outlet. However, with a petrol or diesel-driven compressor, you have total flexibility to set up wherever you need to be without hindrance. Perfect for those semi-professional and professional users.

Standard vs. Oil-less Air Compressors

Oil-less compressors have become increasingly popular for at-home and light DIY use. This table should help you understand the pros and cons of an oil-free compressor vs. a standard-oiled compressor so you can make an informed buying decision.

Compressor Kits

If you’re just starting out on a new hobby, or you want to take the hassle out of the buying process, take a look at our fantastic value bundle offers to get the process started. Whether you’re interested in drilling, ratcheting, wrenching, grinding, stapling, nailing or painting, we'll have the right bundle to kick start even the most ambitious DIY project. Our premium start-up kits ensure you get everything you need at an unbeatable price. Our bespoke bundles are made up of high-quality tools and SGS compressors.