Skip to content
ENExplore Calculators

Oxygen Flow Rate Calculator

Work out oxygen flow rate instantly with clear inputs, formula shown and shareable results.

About Oxygen Flow Rate Calculator

Works backwards from a target inspired oxygen concentration to the flow needed, using the rule of thumb that each litre per minute of nasal oxygen adds about 4%.

Formula

Flow from target FiO2

Flow (L/min) = (target FiO2% - 21) / increment per L/min, with the increment about 4% for nasal cannulae

Worked example

With the default values below, Oxygen Flow Rate Calculator returns Required flow rate of 4.8. Change any input above and every figure here is recalculated in your browser.

Inputs used

Target inspired oxygenaccepts 22–100 %
40 %
Delivery deviceone of Nasal cannula (about 4% per L/min), Simple face mask (about 5% per L/min)
Nasal cannula (about 4% per L/min)

Results

Required flow rate
4.8 L/min
Estimated inspired oxygen at that flow
40%
Oxygen consumption
285 L/h

Step by step

  1. 1Values used
  2. 2Flow from target FiO2
  3. 3Required flow rate= 4.8 L/min
  4. 4Estimated inspired oxygen at that flow= 40
  5. 5Oxygen consumption= 285 L/h

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

How accurate is the 4% rule?

It is only a guide; actual inspired oxygen varies with tidal volume, respiratory rate and mouth breathing.

When is a fixed-performance device needed?

When a precise concentration matters, such as in type 2 respiratory failure, a Venturi mask should be used instead.

Related Calculators

Oxygen Flow Rate Calculator – Calculate Required flow rate