Table of Contents
The right size air compressor comes down to two things: how much air your tools actually need, measured in CFM (cubic feet per minute), and how big a tank you need to keep up with that demand without the compressor cycling on and off constantly. Buy too small and you’ll be waiting on the compressor to catch up mid-job, or watching your tool lose power under load. Buy too big and you’ve spent more than you needed to on a compressor that’s overkill for what you’re actually doing. Crommelins has been supplying portable air compressors to Australian tradespeople and DIY users for decades, and this guide walks through how to work out the size that actually suits your tools and the way you use them.
Start with What You're Actually Running
Every air tool has a CFM requirement listed in its specifications, and this is the number that should drive your compressor choice, not the other way around. A framing nailer or brad nailer generally needs relatively little air, while a die grinder, sander or impact wrench can draw considerably more, especially if it’s running continuously rather than in short bursts. If you’re planning to run more than one tool at once, or want headroom to add tools down the track, add their CFM requirements together and size the compressor to comfortably exceed that total, rather than matching it exactly.
Understanding CFM and Why It Matters More Than Tank Size
It’s a common mistake to shop for an air compressor by tank size alone, but tank size only tells you how much reserve air is stored, not how quickly the compressor can replace air as it’s used. A compressor’s CFM output at a given pressure, usually quoted at 90 PSI, is what determines whether it can keep up with a tool that’s drawing air continuously, like a sander or grinder. For tools used in short bursts, like a nail gun, a smaller CFM output paired with a reasonable tank size is usually fine, since the tank has time to recover between triggers.
Intermittent Use vs Continuous Use Tools
The type of work you’re doing changes what “right sized” looks like. Intermittent tools, like nail guns, staplers and framing tools, draw air in short bursts and give the compressor time to recover in between, so a smaller compressor with a modest tank can handle them comfortably. Continuous-draw tools, like spray guns, sanders, grinders and impact wrenches used for extended periods, need a compressor that can sustain a higher CFM output for longer stretches without the tank running down faster than the compressor can refill it. If most of your work falls into the second category, undersizing the compressor is the mistake to avoid.
Tank Size: How Much Reserve Do You Need?
Tank size determines how much air is available before the compressor needs to catch up, which matters most for tools with sudden demand spikes or when running a tool that needs more air than the compressor alone can supply continuously. Crommelins offers 75 litre diesel models, available with manual or electric start and a three-cylinder cast iron pump rated at 540 litres per minute (19.1 CFM), give more sustained output for bigger jobs or sites without reliable power.
Electric, Petrol or Diesel: Power Source Affects Sizing Too
Where and how you’ll use the compressor affects which power source makes sense, which in turn affects the practical size options available to you. Electric compressors suit workshops and sites with reliable power and are generally the simplest to run and maintain. Petrol models offer the same tank capacity without needing mains power, useful for sites without power access. Diesel models, built for heavier and more sustained use, particularly on construction sites and remote locations, deliver higher continuous output through their three-cylinder pump design, at the cost of being heavier and better suited to being left in one spot rather than moved around constantly.
Sizing for Spray Painting
Spray painting is one of the more demanding applications for a portable compressor, since a spray gun needs a steady, continuous air supply rather than the short bursts a nail gun draws. Undersizing a compressor for spray work usually shows up as inconsistent spray pattern or the finish deteriorating partway through a pass, as the compressor struggles to keep pressure up. For regular spray painting work, it’s worth sizing generously rather than matching the compressor exactly to the gun’s minimum stated CFM, since real-world painting rarely matches a spec sheet’s ideal conditions.
Sizing for Nail Guns and Framing Work
Nail guns and framing tools are comparatively forgiving on compressor size, since they draw air in short, sharp bursts rather than continuously. A 60 litre compressor is generally more than adequate for a single nail gun or framing tool used by one person, giving the tank plenty of time to recover between shots. Where this changes is on a site running multiple nail guns off the one compressor simultaneously, which is where sizing up, or considering a larger diesel unit, starts to make more sense.
Not sure which type suits your load?
Talk to your nearest Crommelins dealer about the right air compressor size, output, power requirements and where you’ll be using it.
Sizing for Workshop and General Trade Use
A general trade or hobbyist workshop running a mix of tools, tyre inflation, impact wrenches, occasional spray work and pneumatic hand tools, generally does well with a mid-sized compressor in the 60 litre range, giving enough reserve capacity and CFM output to cover most jobs without needing to size up to an industrial-scale unit. If your workshop use skews toward continuous-draw tools rather than intermittent ones, lean toward the higher end of that range or consider whether a diesel unit’s higher sustained output better suits how the space is actually used.
Common Sizing Mistakes to Avoid
The most common mistake is sizing to tank litres alone without checking the CFM output against what your tools actually need, which can leave you with a compressor that has plenty of stored air but can’t refill it fast enough for continuous-draw tools. The second most common mistake is the opposite: buying more compressor than needed because bigger sounds safer, when a smaller, lighter, more portable unit would have done the job just as well and been easier to move and store. Matching the compressor to your actual tools and how you use them, rather than guessing on either size, avoids both problems.
Portability Considerations
If you’re moving the compressor between sites or around a property regularly, weight and footprint become part of the sizing decision alongside CFM and tank capacity. If portability matters as much as output, it’s worth checking a model’s actual weight rather than assuming similar tank sizes weigh the same across power source options.
Understanding Duty Cycle Ratings
A compressor’s duty cycle rating tells you roughly what percentage of the time it’s designed to run continuously versus resting to avoid overheating, and it’s worth checking alongside CFM and tank size, especially for heavier or more sustained work. A compressor with a lower duty cycle rating, common on lighter electric units, is designed to cycle on and off as the tank refills, which suits intermittent tools well but can leave it labouring if pushed to run continuously for long stretches. Diesel units, built with heavier-duty pumps like the three-cylinder cast iron design in Crommelins‘ 75 litre range, are generally better suited to higher duty cycle demands, running for longer periods without the same risk of overheating. If your work involves long, continuous runs rather than intermittent bursts, checking the duty cycle rating against your actual usage pattern is just as important as checking CFM and tank size.
Frequently Asked Questions
What size air compressor do I need for a nail gun?
For a single nail gun or framing tool used by one person, a 60 litre compressor is generally more than sufficient, since nail guns draw air in short bursts and give the tank time to recover between shots. If you’re running multiple nail guns simultaneously off one compressor, sizing up or considering a higher-output diesel unit is worth looking at.
Is a bigger tank always better?
Not necessarily. A bigger tank gives more reserve air, but if the compressor’s CFM output can’t keep up with continuous-draw tools like sanders or spray guns, tank size alone won’t solve that problem. It’s better to match both tank size and CFM output to your actual tools than to assume a larger tank fixes an undersized compressor.
Can I run a spray gun off a 60 litre compressor?
It depends on the spray gun’s specific CFM requirement and how continuously you’re spraying. Many 60 litre compressors can handle occasional or light spray work, but for regular, sustained spray painting, checking the gun’s CFM rating against the compressor’s continuous output rating is worth doing before assuming it’ll keep up.
Get the Right Size Compressor from Crommelins
Choosing the right size air compressor comes down to matching CFM output and tank capacity to your actual tools and how continuously you use them, not just picking the biggest or cheapest option available. For diesel compressors with a nationwide dealer network and local support, Crommelins Machinery has a reliable range. Get in touch with your nearest Crommelins dealer to talk through your tools and find the compressor that suits them.
