Gas Cylinder Duration Calculator
Estimate how much usable gas a compressed gas cylinder holds and how long it will last at your flow rate, for calibration gas, purge, nitrogen backup or instrument air bottles.
- Usable gas = n × V × (P₁ − P₂) ÷ Patm ÷ Z = 1 × 50 L × 190 bar ÷ 1.01325 ÷ 1 = 9,376 L
- Duration = usable gas ÷ flow = 1 d 7 h 15 min
Cylinder Contents Formula
Duration = usable gas ÷ consumption
Vwater is the internal (water) volume of one cylinder, P₁ the present gauge pressure, P₂ the lowest pressure your regulator can use, Patm = 1.01325 bar and Z a compressibility correction. At high pressure real gases differ from ideal; the gas supplier states the exact contents of a full cylinder.
Worked example
A 50 L nitrogen cylinder at 200 barg used down to 10 barg holds about 50 × 190 ÷ 1.013 = 9,376 L of free gas, which lasts 31 h 15 min at 5 L/min.
Frequently Asked Questions
What is cylinder water volume?
The internal volume of the empty cylinder, stamped on it (for example 10, 40 or 50 L).
Why use gauge pressure difference?
The gas below the minimum usable pressure stays in the cylinder, so only the difference between present and minimum pressure is available.
Is the ideal gas result accurate?
Close enough for planning at moderate pressure. At 200 bar and above, nitrogen and air hold a few percent less than the ideal value; use the supplier figure for exact contents.
Learn more on the blog
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