How long will an oxygen cylinder last? Duration calculator
For healthcare professionals and students. Check results against your local protocols and clinical judgement; this tool does not give medical advice.
This oxygen cylinder duration calculator estimates how long the oxygen in a cylinder will last at a given flow. Enter the gauge pressure, the flow in L/min and a safety reserve, then describe the cylinder in whichever way you can: a cylinder factor for US-lettered D, E, G and H cylinders, the water capacity stamped on Indian B-type and D-type cylinders, or the full contents and pressure printed on any label. It shows the time to reach the reserve, the time to empty, the litres left and a table for other flow rates.
It is meant for nurses, paramedics, respiratory therapists and students planning a transfer or checking a portable cylinder. Pressure can be entered in psi, bar, kgf/cm², kPa or MPa, and switching units converts the numbers already typed.
How to use the Oxygen Cylinder Duration Calculator
- Choose how to describe the cylinder: Cylinder factor, Water capacity or Label contents.
- Pick the cylinder size or type, or enter the factor, water capacity or label values yourself.
- Read the gauge pressure and choose its unit.
- Set the safety reserve your service uses (0 to run the calculation to empty) and the flow rate in L/min.
- Read the time until the reserve, the time to empty and the table for other flows; copy the result for the handover.
Oxygen Cylinder Duration Calculator features
Three ways to describe a cylinder
US cylinder factors, water capacity (Indian B/D-type or any stamped value) or label contents and pressure.
Any pressure unit
psi, bar, kgf/cm², kPa or MPa, converted exactly (1 psi = 6.894757 kPa, 1 kgf/cm² = 98.0665 kPa).
Safety reserve
Subtracts a reserve pressure you choose and shows both time-to-reserve and time-to-empty.
Flow table
Durations at 1–15 L/min so you can plan if the prescription changes.
Checks
Warns about readings at or below the reserve, implausible pressures, unit slips and very high flows.
Oxygen cylinder duration formula
For cylinders with a factor: minutes = (gauge pressure − reserve) in psi × cylinder factor ÷ flow (L/min). The factor is the full volume divided by the full pressure. The Tampa General Hospital oxygen-duration guide works two examples that the self-test reproduces: an E cylinder at 1,500 psi × 0.28 ÷ 2 L/min = 210 minutes, and 1,000 psi × 0.28 ÷ 10 L/min = 28 minutes (both without a reserve).
For a cylinder described by water capacity, Boyle’s law gives the free gas at atmospheric pressure: litres ≈ water capacity × gauge pressure (bar) ÷ 1.01325. A 46.7 L cylinder at 150 bar holds about 6,913 L. This ignores the compressibility of oxygen at high pressure, so it slightly underestimates a full cylinder — the safe direction. For a cylinder label, litres = label contents × gauge ÷ label full pressure.
Cylinder factors and capacities used
The US cylinder table is from the Special Operations Medical Guide 2023, “Oxygen cylinder life”. M cylinders are not offered as a preset because published factors disagree (1.36 and 1.56 L/psi both circulate in teaching material); use “Other” with the factor for your supplier’s cylinder, or the label mode. UK and European cylinders are usually labelled with their contents in litres and full pressure in bar — use the label mode.
| Cylinder | Value used | Full contents | Source (checked 19 Oct 2026) |
|---|---|---|---|
| D (US lettering) | 0.16 L/psi | ≈ 356 L | SMOG 2023 table; TGH guide (350 L) |
| E (US lettering) | 0.28 L/psi | ≈ 622 L | SMOG 2023 table; TGH guide (625 L) |
| G (US lettering) | 2.41 L/psi | ≈ 5,260 L | SMOG 2023 table |
| H / K (US lettering) | 3.14 L/psi | ≈ 6,900 L | SMOG 2023 table |
| India D-type | 46.7 L water capacity, 150 kgf/cm² | ≈ 7,000 L | Gujarat Commissionerate of Health specification, 2021 (IS 7285 Part II) |
| India B-type | 10.2 L water capacity (10.2–15 L sold) | ≈ 1,500 L | AIIMS Raipur specification (IS 7285 Part 2) |
Practical points
- Reserve: many services stop at about 200 psi (14 bar) so a cylinder is never run dry; set the value your policy uses.
- Ventilators and high-flow devices use more gas than the dial suggests. The TGH guide notes that bias flow must be added to the patient’s minute volume, and that a lower FiO₂ uses less cylinder oxygen.
- Gauges are approximate, especially near empty, and cold cylinders read low. Recheck the gauge during long transfers.
Oxygen Cylinder Duration Calculator FAQ
How long does an E cylinder last at 2 L/min?
At 2,000 psi with a 200 psi reserve, (2,000 − 200) × 0.28 ÷ 2 = 252 minutes, a little over 4 hours. Run to empty, the same cylinder lasts about 280 minutes.
How is oxygen tank duration calculated?
Multiply the usable pressure by the cylinder factor to get litres, then divide by the flow in L/min. The oxygen cylinder duration calculator does this and shows the working.
How many litres are in a D-type oxygen cylinder in India?
About 7,000 litres when full: 46.7 L water capacity at 150 kgf/cm². The water-capacity mode estimates the contents from the actual gauge reading.
What is a cylinder factor?
The litres of gas released for each psi of gauge pressure: full contents divided by full pressure. For an E cylinder it is about 0.28 L/psi.
Why subtract a reserve?
Gauges are least accurate near empty, and a cylinder that runs dry mid-transfer is dangerous, so most services change it before it is empty. Set the reserve to 0 to see the time to empty.
Can I use bar instead of psi?
Yes. Choose bar, kgf/cm², kPa or MPa; values already typed are converted.