What is the formula used?

The calculator uses Boyle's Law: V_available = (P_gauge / P_atm + 1) × V_cylinder. This gives the total oxygen volume at atmospheric pressure. Duration (minutes) = V_available / flow_rate_LPM.

Should I enter gauge pressure or absolute pressure?

Enter gauge pressure — the reading shown on the cylinder regulator gauge. The calculator automatically adds atmospheric pressure (14.696 PSI or 1.01325 bar) to convert to absolute pressure for the calculation.

What is cylinder water volume?

Water volume (also called internal volume or capacity) is the total internal space of the cylinder in liters. It is stamped on the cylinder shoulder and is different from the gas capacity. Common sizes: E cylinder ≈ 4.7 L, H/K cylinder ≈ 49 L.

Why does the result differ from manufacturer charts?

Manufacturer charts typically assume the tank starts at full rated pressure. This calculator uses the actual current pressure you enter, so it reflects real remaining supply. Slight differences may also arise from residual pressure left in the tank (typically 200 PSI / 14 bar is considered empty for safety).

What safety margin should I use?

Medical guidelines often recommend treating a cylinder as empty when gauge pressure drops to 200 PSI (13.8 bar). Always plan to change or refill before this threshold.

Can I use this for non-oxygen gases?

The duration calculation works for any compressed gas where flow rate is measured in LPM, but the tool is optimized for oxygen. For other gases, verify that your flow rate units match liters per minute at atmospheric pressure.

Oxygen Tank Duration Calculator

Name: Oxygen Tank Duration Calculator
Availability: InStock
Author: Nham Vu

Enter tank pressure, cylinder volume, and flow rate to instantly calculate how long your oxygen supply will last.

Cylinder Parameters

Units:

Current Tank Pressure (PSI gauge)

Reading shown on the regulator gauge.

Cylinder Water Volume (liters)

Internal capacity stamped on cylinder shoulder.

Flow Rate (liters per minute)

Prescribed or set delivery rate in LPM.

Quick Cylinder Presets

Enter cylinder parameters and click Calculate Duration.

Summary

Enter tank pressure, cylinder volume, and flow rate to instantly calculate how long your oxygen supply will last.

How it works

Enter the current tank pressure in PSI or bar.
Enter the cylinder water volume (internal capacity) in liters or cubic feet.
Enter the oxygen flow rate in liters per minute (LPM).
The calculator converts gauge pressure to absolute pressure and applies Boyle's Law to find total available oxygen at atmospheric pressure.
Duration is computed by dividing available oxygen volume by the flow rate and displayed in hours and minutes.

Use cases

Estimate home oxygen therapy supply time before a refill is needed.
Plan oxygen reserves for emergency medical services and first responders.
Calculate industrial welding or cutting gas duration before bottle swap.
Verify oxygen supply adequacy for a patient transport or ambulance run.
Budget oxygen usage during dive or confined-space rescue operations.
Pre-flight oxygen planning for general aviation pilots.
Hospital ward oxygen bottle management and rotation scheduling.
Training exercises where oxygen consumption must be tracked.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu