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Oxygen Tank Duration Calculator

Estimates how long a compressed-gas oxygen cylinder will last from its gauge pressure, size-specific conversion factor (litres per psi), a safe residual pressure and the flow rate.

When to use

You need to plan transport or home oxygen supply from a D, E, M, G or H/K cylinder at a continuous flow.

Do not use when: The device is a liquid-oxygen reservoir or concentrator, or the flow is pulse-dose (conserving device), where duration depends on breath rate rather than continuous flow.

Formula

duration_minutes = (pressure_psi − safe_residual_psi) × cylinder_factor / flow_l_per_min; factors: D 0.16, E 0.28, M 1.56, G 2.41, H/K 3.14 L/psi

Factors are the cylinder's full capacity divided by its service pressure (about 2,000–2,200 psi) and assume ideal-gas behaviour at room temperature; cold cylinders and regulator leaks shorten the real duration. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Unit	Required	Description
`cylinder_size`	enum: d \| e \| m \| g \| h_k		yes	US cylinder size letter; sets the conversion factor in litres of gas per psi.
`pressure_psi`	number	psi	yes	Current cylinder gauge pressure (bar × 14.5). Range: ≥ 0, ≤ 3000
`flow_l_per_min`	number	L/min	yes	Continuous oxygen flow. Range: > 0, ≤ 60
`safe_residual_psi`	number	psi	default 200	Pressure reserved so the cylinder is never emptied (commonly 200 psi; 500 psi in some services). Range: ≥ 0, ≤ 1000

Outputs

Output	Type	Unit	Description
`cylinder_factor_l_per_psi`	number	L/psi	Litres of gas released per psi for this cylinder.
`usable_oxygen_liters`	number	L	(pressure − safe residual) × factor.
`duration_minutes`	number	min	Usable litres / flow.
`duration_hours`	number	h	Same duration in hours.
`duration_formatted`	string		Hours and minutes.

Example

E cylinder, 2000 psi, 2 L/min, 200 psi reserve: {"cylinder_size":"e","pressure_psi":2000,"flow_l_per_min":2,"safe_residual_psi":200} → {"usable_oxygen_liters":504,"duration_minutes":252,"duration_hours":4.2,"duration_formatted":"4 h 12 min"}

D cylinder, 1500 psi, 4 L/min: {"cylinder_size":"d","pressure_psi":1500,"flow_l_per_min":4} → {"cylinder_factor_l_per_psi":0.16,"usable_oxygen_liters":208,"duration_minutes":52}

GET https://tttkmbb.com/api/v1/calculate/oxygen-tank-duration?cylinder_size=e&pressure_psi=2000&flow_l_per_min=2&safe_residual_psi=200

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/oxygen-tank-duration (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/oxygen-tank-duration · Markdown: https://tttkmbb.com/medical/oxygen-tank-duration.md · JSON definition: https://tttkmbb.com/medical/oxygen-tank-duration.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="oxygen-tank-duration"
OpenAPI operationId: estimate_oxygen_tank_duration
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Hardavella G et al. (2019) Oxygen devices and delivery systems, Breathe 15:e108-e116 (peer_reviewed)
Respiratory Therapy Zone – Oxygen tank duration formula and cylinder factors (reference)

FAQ

Why subtract a safe residual?

Regulators become unreliable near empty and a cylinder must never run dry during transport; 200 psi is a common reserve, some protocols use 500 psi.

What about pulse-dose conservers?

They deliver oxygen only on inspiration and typically extend duration 2–4 times; the manufacturer's conserving ratio is needed to convert.

Related calculators

IV Drip Rate Calculator — Another time-and-flow calculation for clinical supplies.
Pressure Converter — Convert cylinder pressure between psi and bar.