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Oxygen Cylinder Remaining Volume & Duration Calculator

Quickly estimate the remaining gas volume and how long an oxygen cylinder will last from its capacity, pressure and flow rate.

Input

Estimate the remaining gas volume and usable time of an oxygen cylinder from its capacity, pressure and flow rate. Remaining gas is inferred from the pressure ratio, so actual supply time varies with the device and regulator.

Cylinder capacity (nominal)
L
MPa
MPa
L/min

Typically 0.8 (treats 80% of the remaining gas as usable)

Result

Usable time (safety factor 0.8 applied)

136min

About 2 h 16 min (flow 2.0 L/min)

Remaining gas

340 L

Remaining ratio

68 %

Usable gas

272 L

Calculation breakdown

Cylinder capacity (nominal)500 L
Full-charge pressure14.7 MPa
Current pressure10.0 MPa
Remaining gas (capacity × current ÷ full pressure)340 L
Safety factor0.8
Usable time2 h 16 min

How it works

  • Remaining gas (L) is calculated as nominal cylinder capacity (L) × current pressure ÷ full-charge pressure. Gas volume is taken to be roughly proportional to pressure, so the remaining amount is estimated from the ratio of the gauge readings.
  • Usable time (min) is calculated as remaining gas (L) × safety factor ÷ flow rate (L/min). A safety factor of 0.8 is commonly used (treating up to 80% of the remaining gas as usable) to keep a margin before the cylinder runs empty.
  • A typical medical cylinder example is 500 L capacity at a full-charge pressure of 14.7 MPa. Check the actual capacity and full-charge pressure on the cylinder's stamping or label before entering them.
  • The remaining ratio is shown as current pressure ÷ full-charge pressure. Because the current pressure changes with flow, temperature and remaining volume, entering the gauge reading taken just before use improves accuracy.
  • This tool is an approximation based on the pressure ratio and does not account for regulator type, ambient temperature or equipment losses. The calculated time is only a guide and the actual supply time will vary, so plan for early replacement and keep a spare on hand.
  • This tool provides estimates from a general formula and is not a diagnosis or medical advice. Always consult a physician for health-related decisions.