How to Choose the Best Air Compressor for the Job

Here at SGS, we have a huge range of professional and DIY air equipment for numerous applications and requirements. We understand that it might seem daunting to try and pair your air tools with a specific air compressor, especially when the range of choices is so broad. The best air compressor is always the right air compressor for the job, so we've put together a simple user guide to help you make an informed decision about which compressor is worth your investment, as well as a check list of of considerations to help you narrow the field.

What You'll Need to Consider: Quick Start

  • Your CFM requirement - probably the single biggest consideration when buying a compressor. What CFM will your air compressor need to produce in order to power all of your air tools?
  • Choosing a tank size - with tank sizes ranging from 6 litres to 500 litres+, choosing the perfect capacity air tank / receiver will seriously affect the performance of your compressor.
  • Oil-less or oil compressor - oil-less compressors are low maintenance and free from contaminants, however a standard compressor will produce a larger output and run quieter.
  • Professional, semi-professional or domestic use - all compressors comes with specific warranties to cover either DIY/home use or continuous commercial use. Make sure you choose the right compressor for your application.

Why Use an Air Compressor Rather than Another Power Source?

Choosing to use compressed air as a power source has many distinct benefits, rather than say electricity. Air power is becoming increasingly popular for the use in the homes as well as larger, more industrial settings like workshops and garages.

Lower Weight & Ergonomic Tools

Air tools tend to be far more light weight and smaller than battery or mains powered tools, purely because they don’t need to be fitted with a heavy motor or battery cells. A huge variety of air tools are available and they can all be affixed to one central power source and swapped around as require.

Safer Than Electricity

There’s many settings where electric powered tools can’t be used because of the risk of electrical fires or the possibility of operator electrocution. Air tools are safer, simply because they contain no electrical elements meaning there is nothing that can go wrong electrically and potential harm the user. If you work in a moist or damp area, or if there’s combustible gases around, you might use air tools and a compressor to keep working conditions safe - making air tools suited to numerous working environments.

More Economical

Air tools are (almost) always cheaper than electric of hydraulic tools, meaning you can build up a collection of quality tools without breaking the bank. In commercial settings you’ll find that air systems are easier and less costly to install than hydraulic systems or upgrading your electric supply. Air tools themselves have considerably lower maintenance requirements, meaning less downtime.

Understanding Required Air Flow

The most important consideration when purchasing a new air compressor is the air flow the compressor can deliver. Air tools have certain requirements to run at optimum capacity and the most important is Required SCFM or Standard Cubic Feet per Minute.

All air tools will have a required SCFM, but in general smaller air tools require between 0-5 SCFM, while larger tools can need 10 or more SCFM.

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Working out your CFM requirement

The first thing you need to work out is how much air will you need to power your air compressor tool? To work this out we need to know how much air flow the compressor can produce and how much air flow an air tool requires to run .

  1. Find the required air flow (SCFM)
    of your air tools. This information will be in your tools user guide or manufacturers website.
  2. If you’re going to be running multiple tools at the same time you’ll need to add together the individual required SCFM of each tool. Most DIY compressors are designed to run only one tool at a time, however you can normally successfully run several tools simultaneously with 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

For 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 a rough guide only. Larger compressors with higher CFM and bigger tanks will always give you better performing tools that can be used for longer, so it's normally worth buying the largest compressor in your budget.

Typical SCFM Requirements

These are just typical value of various air tools. You should always check with exact requirement of your tool by consulting your user guide.

Tool Type Req. SCFM's Tool Type Req. SCFM's Tool Type Req. SCFM's
Angle Disc Grinder 6 SCFM Dual Action Sander 6 SCFM Ratchet 1/4" 3 SCFM
Air Drill 1/2 4 SCFM Grease/caulking Gun 4 SCFM Ratchet 3/8" 4 SCFM
Air Drill 3/8 4 SCFM High Speed Grinder 5" 4 SCFM Sand Blaster 4 SCFM
Butterfly Impact 3 SCFM Impact Wrench 1/2" 5 SCFM Spray Gun 6-18 SCFM
Air Hammer 4 SCFM Impact Wrench 3/4" 7 SCFM Straight Line Sander 7 SCFM
Cut Off Tool 4 SCFM Nailer 1 SCFM
Die Grinder 8 SCFM Orbital Jitterbug Sander 6 SCFM

Measuring Air Compressor Power & Flow Rate: CFM, FAD, Lt/min

There’s loads of different ways of talking about the power of an air compressor and a huge array of terms and abbreviations involved. We thought it was worth listing all the different ways you can measure air compressor power, any associated abbreviations and what the terms actually mean.

Flow Rate: CFM and Lt/min

CFM stands of Cubic Feet per Minute and is the imperial unit of measurement for describing the air flow rate of a compressor. The metric equivalent of CFM is Litres per Minute (or Lt/min). The imperial measurement of CFM is used more widely than litres per minutes, so you’re more likely to encounter CFM than Lt/min.

You’ll probably see CFM being used in two different ways; the first is CFM (displacement) and the second is CFM (FAD) -  so you’re probably wondering what, what is the difference between CFM (FAD) and CFM (Displacement)?

Cubic Feet per Minute Displaced - CFM (displacement)

This measurement is the theoretical, nominal capacity of an air compressor’s pump. This unit is actually measuring what is being drawn into the air compressors pump, i.e. what the pump could theoretically displace assuming 100% efficiency. The figure is worked out based on the size of the pump’s cylinders and speed the pump operates at. In practice, the CFM (displacement) alone is only a rough estimate of how much air will actually be displaced and therefore you need to take this into account when pairing a compressor with your air tools.

Cubic Feet per Minutes, Free Air Delivery - CFM (FAD)

This unit of measurement is far more useful because it’s looking at the volume of air actually discharged from the air compressor to the output (i.e your air tools). FAD is far more useful the CFM (displacement) as you can see the actual “power” a compressor has available for tools etc.

CFM (FAD) is typically a third less than CFM (Displacement), so if your air compressor is advertised as 10 CFM (displacement), then the Free Air Delivery (FAD) is probably around 6.6 CFM.

Air loss through hoses and fittings

air-lose Air flow is lost through air hoses, hose fittings, filters, lubricators, and especially through quick-connect couplings. If you plan to run your air tool some distance away from the actual compressor or with any of these peripherals, you may need to consider this pressure drop when choosing a compressor. The more CFM your compressor produces, the better your tool will run with longer hoses and more fittings.
Exclamation TOP TIP: Never use extension leads with an air compressors! The voltage drop from an extension cable can damage the air compressor motor. Instead use a longer air hose.

Working Pressure

ManifoldThe pressure generated inside the tank of an air compressor is measured in Bar and Pounds Per Square Inch – or PSI. Most compressors will have a working pressure of 8 bar / 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 what working pressure is required for your air tool by looking at the user manual or contacting the manufacturer.

 

Receiver / Air 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.

Working out your required tank size

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

For example, if you want to 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.

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6 litre compressors

High performance, compact and portable air compressors, used for smaller projects like spray painting, nailing/stapling and tyre inflating. These compressors are completely oil-less and low maintenance. View Now

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24 litre compressors

Our range of 24 litre compressors provide great value for money and a fair sized tank for slightly larger jobs. With SGS and Nuair brand compressors available, you can pick a great DIY compressor or something for more professional use. View Now

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50 litre compressors

We stock portable and stationary compressors with 50 litre receivers for hobby and professional use. With a larger tank, you’ll be able to handle medium sized air tools and more demanding applications. View Now

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100 litre compressors

This range of large capacity compressors includes electric and petrol powered options, suitable for domestic, semi-professional and commercial use. Spend less time waiting for your receiver to fill up, and more time using your air tools. View Now

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200+ compressors

Ranging from 200-500 litres, these huge capacity compressors are great for commercial and workshop applications. They’re all stationary compressors with anti-vibration mounts and you can choose between an electric, petrol or diesel power sources. View Now 

Standard vs. Oil-less Air Compressors

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

Standard (Oiled) Air Compressors

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Oil-less Air Compressors

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Lubrication Standard air compressors use a lubricating oil to effectively and reliably to keep the pistons moving in a good working order. In oil-less compressors the pistons are permanently pre-lubricated in a material such as Teflon. This means, in effect, you don't need to worry about lubrication with an oil free compressor.
Maintenance The oil will need changing periodically in your oiled compressor to ensure it runs consistently and correctly. Neglecting the Maintenance schedule may cause irreversible damage to your unit and invalidate your warranty. No oil means no oil changes, meaning minimal maintenance requirements.
Weight Standard compressors weigh considerably more than oil-free compressors as a rule. Oil-less compressors require less parts, meaning (in general) they tend to be a lot lighter weight than standard alternatives. This tends to keep the cost down too.
Usage  While oil-free compressors might be more lightweight, cheaper and require less maintenance, standard compressors are more durable and hardwearing. Most industrial and commercial air compressors will utilise oil. If you’re a serious home user you'll probably want to invest in a oiled compressor. The Teflon coated cylinders will get worn down over time, meaning your piston will start to get dry and performance will suffer. Oil free compressors are very popular with light to medium home users.
Noise Standard compressors tend to be a lot quieter than oil-less alternatives, purely because they're liquid lubricated. This probably wont matter if you're using the compressor infrequently, however if a quiet working environment is important to you, we'd suggest a standard compressor.
Contaminates  Having an oiled compressor means there's a chance of getting contaminates in your air line. This isn't so much of an issue for most air tools, however if you're using a spray gun, it could ruin your work. This can be over come by using an air filter before your air tool. No oil means no contaminates, making these compressors popular with spray painters and clinical settings.

DIY or Professional Use?

Professional Air Setup We split our range of compressors into two specific ranges; DIY and professional use – each with it’s own specific warranty tailored for it’s intended use.

If you’re a DIY user, hobbyist or occasional user of an air compressor, we’d suggest a SGS compressor. Fantastically 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. They've been designed with the DIY user in mind and are perfect for working in the garage at the week end or 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. Nuair and Fini Pro compressors are designed for a variety of applications. We stock professional portable compressors, perfect for service engineers, upholsterers and other mobile users, as well as stationary compressors for workshops and industrial settings. Hyundai compressors offer great value for money and are perfect for professional (or semi-pro) users with lighter requirements.

SC24H-LeftSemi-Pro Compressors
Our range of compressors are designed for home use, hobbyists, and semi-professional applications. They’re great value for money and perfect for someone wanting to use a compressor occasionally. With two years domestic warranty and free delivery on orders over £50 – these compressors are amongst the best in the consumer market. View Now

S-N7TN9R1NUAProfessional compressors
Perfect for workshop and industrial set ups, these compressors offered by Hyundai, Nuair and Fini come with anti vibration feet for minimal noise pollution, and large receiver / air tanks for heavy duty usage. View Now

 

What’s the Difference Between Reciprocating & Rotary Screw Air Compressors?

The two most popular air compressor types are the reciprocating air compressors and rotary screw compressors. If you’re looking for a compressor for a commercial setting, you’ll have to decide which type is right for you (DIY/home users will always want a reciprocating compressor).

Reciprocating compressors - The reciprocating compressor compresses air with the use of one or more cylinders/pistons. The pistons move up and down (reciprocating) inside the cylinders to compress the air.

They range from low to very high pressure and tend to come with low capacity tanks. They’re designed for intermittent use and are often used in workshops, garages, DIY settings and nailing on construction sites.

Rotary screw compressors – these compressors compress air via two screws or rotors that turn in different directions within the housing. The trapped air is compressed and stored in the receiver. They tend to be lower pressure by far higher capacity than reciprocating compressors. They can be used pretty much continuously and are huge industrial machines.

They can be powered by huge motors (100HP+). Buy a rotary screw compressor if you need access to air all the time, such as in a large workshop, factory or industrial setting. If your

compressor is going to be standing still more than 60% of the time, it’s normally better to get a reciprocating compressor.

Electric, Petrol or Diesel

When you start looking at the more professional air compressors you’ll start seeing a larger variety of power options. You might want a 400V, three-phase power supply for a commercial setting, or a petrol/diesel compressor for more flexibility.

petrolPetrol and Diesel Powered Compressors With a conventional electrical air compressor you’ll always be limited with where you can set up and get on with your project as you need to be near a mains power outlet. With a petrol or diesel driven compressor you have the flexibility set up wherever you need to be without hindrance. Perfect for semi-professional and professional use.  View Now

Quick Start Bundles from SGS

If you’re just starting out on a new hobby, or you want to take the hassle out of the buying process, here at SGS we have a range of fantastic value bundle offers to get the process started. Whether you’re interesting in getting in to drilling, ratcheting, wrenching, grinding, stapling, nailing or painting, we'll have the right bundle to kick start even the most ambitious DIY project. With bespoke bundles made up of high quality tools and SGS compressors, all delivered free to the UK mainland, our special offers page is a great way to begin the buying process.

SC6H-K56 litre air compressor and nail & staple gun kitour 6 litre, 5.7 CFM oil-less compressor is a fantastic low maintenance compressor anyway, but when you pair it with the SAT403 air nail and staple gun you get a really special, powerful tool combination. Great for upholstery, and home maintenance tasks, this bundle makes an ideal starter pack. Air hose, couplers and gauge included. View Now

 

SC24H-K224 litre air compressor and spray kitthe plucky SGS 24 litre, 9.6 CFM compressor comes fully equipped with a HVLP gravity fed professional spray gun, 10m rubber air hose, regulator with gauge, mini air filter and water trap and 2 euro quick couplers – everything you need to start spray painting. View Now

 

 

SC100V-K3100 litre air compressor and 71 piece Tool Kit – As well as a high capacity 14.6 CFM air compressor with 3.0HP motor, you receive an array of tools and accessories including; Impact Wrench, Die Hammer, Ratchet & Grinder, two rubber hoses with quick release couplers, air filter, water trap, regulator and lubricator, compressor oil, air line oil and all the couplers you’ll need to get started. View Now

 

SC24H-K1Great vale bundle offersSee the full range of great value tools and compressor bundles and find exactly that right starter pack for you. With free, next day delivery on all the bundles in the range (UK mainland), you can start using you air compressor for less. Set up examples and how-to diagrams are shown on the product pages, and every product is shipped with detailed instruction manuals. View Now

Glossary of Key Compressor Terms

Here at SGS we understand that all the jargon surrounding air compressors can be an obstacle when choosing a compressor. We've taken the time to explain some of the key terms you'll come across when shopping for a compressor.

Displacement (Volume) - The displacement of a compressor is the theoretical capacity of a compressor, i.e. the swept volume of a cylinder multiplied by the number of compressions per minute. This is normally expressed in CFM (Cubic Feet Per Minute).

Free Air Delivered - This measurement describes the volume of air taken in to a compressor and therefore accurately describes the usable volume of air. Normally this is expressed as FAD/CFM.

Pressure - This is the force / power in the compressed air system. This will be expressed in PSI or bar. The maximum pressure is important because if you have too low a pressure your air equipment will not work correctly. If the pressure is too high it will quickly wear out your air equipment, or at worst, make the equipment dangerous to use. Most compressors will allow you to regulate the working pressure for the equipment you're using.

Single Stage Compressor -  One or more cylinder produces the final pressure in a single compression. The normal maximum working pressure of a single-stage compressor is 145-150 PSI.

Two Stage Compressor  - Air is compressed to around 30 PSI, cooled down and then compressed to the final pressure in the 'second stage'. The normal maximum working pressure is up to 200 PSI. Two stage compressors give you a higher output with less energy consumption.

Air Leakage - Old hoses with small leaks create a huge loss in output and cost a small fortune in the long run. For example, a 0.75mm dia. air leakage is a loss of 1.6 CFM or an extra 300W of energy. A 1.4mm dia. hole is a loss of 6.5 CFM or 1100W! Replace faulty equipment quickly to avoid mounting costs and a lack of performance.

Single phase - A standard domestic power supply of 220/240 volts. Single phase compressors normally have under 3.0HP electric motors.

Three phase - Ideal for industrial / commercial use. 380/440 volt power supply with no upper limit of motor size. You get around a 2/3 cost saving when compared to a single phase alternative. The stable power supply helps extend the life of the electric motor.

Still not sure which compressor to choose?

iconAs well as designing our own range of air compressors and tools, SGS engineering works closely with various suppliers to ensure we only stock the very best air solutions. Our in house expert are always on hand for buying advice and to provide bespoke care, regardless of the application. Whether you’re just starting out on a new hobby or you have complicated commercial requirements, we’ve got the in-house experts to help. Call SGS on 01332 576 850 or fill out our contact form today, for all the purchasing advice and support you need.