- Author
- Byron Raal, CAS Founder-Editor About the author
- Date last checked
- 10 September 2026
How do I size an air compressor for my plant? Start with the flow your tools and processes need, identify which uses overlap, and record short peaks as well as normal demand. This calculator adds your stated leakage and growth allowances to a planning flow estimate. Pressure, inlet temperature and elevation travel with that estimate for the supplier to check against a particular compressor. It does not turn an air-density rule into a guaranteed nameplate rating.
Air Compressor Sizing Calculator
Flow is shown in L/s, CFM and m³/min on the same reference basis as your input. Changing units does not convert inlet conditions or verify that a catalogue figure is Free Air Delivery (FAD). Pressure is bar gauge. Confirm every input’s reference conditions before comparing it with compressor performance.
How this calculator works
Planning flow = audited demand × simultaneous-demand factor × (1 + leakage allowance) × (1 + growth allowance). The two allowances are fractions of the preceding result. These are your planning assumptions, not standard percentages prescribed by ISO 1217. If measured system demand already contains leakage or coincident use, avoid counting that adjustment again.
For example, 100 L/s of audited demand with a supported 0.50 simultaneous factor, a 10 per cent leakage addition and 20 per cent growth gives 100 × 0.50 × 1.10 × 1.20 = 66 L/s. This is an arithmetic example. It does not identify a compressor motor size or establish that 66 L/s will cover a particular plant’s bursts, control cycle or air-treatment losses.
A short burst can need more air than the average load. Give the supplier its flow, duration, repetition and minimum acceptable pressure, together with the compressor contribution and available storage. Receiver size and control settings need their own check; an average demand figure cannot settle them.
Why there is no generic temperature or pressure multiplier
The effect of inlet pressure, temperature and humidity varies with compressor design, drive and cooling conditions. Atlas Copco’s high-altitude guidance calls for the specific equipment and air-consumption conditions to be assessed. A simple density ratio is not a verified capacity correction for every compressor.
CAGI’s performance guidance and data sheets provide a way to compare reported package performance at stated operating points. ISO 1217 specifies displacement-compressor acceptance tests. Neither makes this calculator a supplier-approved equipment selection. Ask for the offered model’s delivered flow at your required discharge pressure, with its inlet/reference basis, site limits and package power stated.
What to send with a quote request
Supply the demand basis and measurements, working schedule, peak duration, point-of-use pressure, likely pressure losses, inlet temperature range, elevation and air-quality requirement. Ask the supplier to explain storage, dryer/filter selection, control range and energy performance for that profile. Compare the available package data, not motor kW or swept volume alone.
If you are comparing technologies, the air compressors hub and rotary screw versus piston guide provide background. The written sizing guide covers the wider workflow; verify any rule of thumb against the offered equipment. The result here is a demand estimate, not an automatic capacity correction.
Get the two-page sizing worksheet to record your demand profile, short peaks, site conditions and the supplier checks still needed. It separates measured facts from planning allowances and equipment selection. Email only, and the download is on the next screen.
Want to discuss a supplier introduction? Tell us what you are sizing. If a suitable Australian supplier is available, we will ask for your written permission before sharing your details. Any referral payment arrangement will be explained before you decide. An introduction is not guaranteed.
Independent and vendor-neutral. No obligation, and no sales calls from us.
Form not loading? Email byron@compressedairsolutions.com.au with your worksheet request.
Frequently asked questions
What is Free Air Delivery (FAD) and why does this calculator use it instead of CFM or kW?
FAD expresses delivered air as an equivalent volume flow at stated inlet or reference conditions. CFM and L/s are flow units; either can describe FAD when the basis is specified. kW is power. Confirm the operating pressure and reference conditions when comparing ratings. This tool preserves your input basis and converts units only.
Why does the calculator ask for my site's ambient temperature and elevation?
They are part of the site conditions the supplier needs to verify the offered model. The calculator records inlet design temperature and elevation with the result. It does not apply a fixed temperature, altitude or pressure multiplier or claim a resulting nameplate capacity.
Can I use this calculator if I do not know my exact tool-by-tool demand yet?
You can explore an explicitly assumed demand, but the calculator cannot supply a missing tool audit. Its factor options are planning scenarios, not validated industry presets. Obtain a measured demand profile or equipment consumption data before making a purchase decision.
Does this calculator replace a supplier's own sizing quote?
No. It organises a planning demand estimate and the site conditions for review. A suitable supplier or engineer must check the offered equipment, peak demand, storage, controls and air treatment for the actual installation.
Is this calculator method accepted by Australian compressor suppliers?
CAS has not established supplier approval of this calculator. Ask the quoting supplier to verify the input basis, allowances and equipment performance, and explain any different recommendation. ISO 1217 is an acceptance-test standard, not certification of this planning tool.
General information only. This calculator provides a planning estimate from the inputs you enter. It is not engineering, safety or professional advice. Have compressed air system design and equipment selection checked for your plant before purchase. Read the full disclaimer.