Calculators · Hydraulics and pneumatics

Air compressor sizing, tank fill time and air leak cost calculator

Compressed air is one of the most expensive forms of energy in a workshop or factory: most of the electricity a compressor uses ends up as heat. These calculators size a compressor for the tools it must run, estimate how long it takes to fill a receiver tank, and show what a leak is costing you each year — often the cheapest saving available.

Compressor capacity for your tools

Adds up the air each tool uses, weighted by how much of the time it actually runs, then adds a margin for leaks and future tools. Compare the result with the compressor’s free air delivery (FAD), not its displacement.

Results
Required free air delivery—L/minMinimum FAD the compressor should provide.
Required free air delivery—CFMThe same in cubic feet per minute.

Formula
demand = Σ (tool flow × duty)
required = demand × (1 + margin)

Receiver tank fill time

Estimates how long a compressor takes to pump a receiver tank from one pressure to another. It assumes the compressor delivers its rated free air delivery throughout; real output falls somewhat as pressure rises.

Results
Fill time—minutesTime to reach the final pressure.
Free air stored—LAtmospheric air pumped into the tank.

Formula
free air = V × (p₂ − p₁) / p_atm
t = free air / FAD

Annual cost of an air leak

Estimates the air escaping through a leak of a given size and the electricity needed to replace it. Leaks typically waste 20–30% of a plant’s compressed air; a single 3 mm leak can cost more than a thousand a year.

Results
Leak flow—L/sFree air escaping, assuming a sharp-edged hole (Cd 0.65).
Energy wasted per year—kWhElectricity used to replace the lost air.
Cost per year—currencyEnergy wasted multiplied by electricity price.

Formula
ṁ = Cd × A × p₀ × √(k / RT) × (2/(k+1))^((k+1)/(2(k−1)))
energy = free air × hours × specific energy

Worked example: a small workshop

  1. An impact wrench (300 L/min, 40%), blow gun (150 L/min, 25%) and sander (500 L/min, 10%) average 207.5 L/min.
  2. With a 30% margin, choose a compressor delivering at least 270 L/min (about 9.5 CFM) free air.
  3. A 250 L/min compressor fills a 200 L tank from empty to 8 bar in about 6.3 minutes.
  4. A 3 mm leak at 7 bar, pressurised 4,000 hours a year, wastes about 7.2 L/s, or roughly 11,400 kWh — about 1,700 a year at 0.15 per kWh.

Typical air consumption of tools at 6.3 bar

ToolAir consumption
Blow gunabout 100 – 200 L/min
½-inch impact wrenchabout 150 – 300 L/min
Air ratchetabout 100 – 150 L/min
Random orbital sanderabout 300 – 500 L/min
HVLP spray gunabout 250 – 450 L/min

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About these results

Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.

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