Fire Extinguisher Sizing Calculator

Work out fire extinguisher sizing instantly with clear inputs, formula shown and shareable results.

About Fire Extinguisher Sizing Calculator

The usual rule provides one 13A rated unit per 200 square metres of light or ordinary hazard floor space, doubled for high hazard, with a minimum of two per floor and no more than 30 metres travel distance. The travel distance limit often drives the count more than the area rule, because a long thin floor plan needs extra units to keep everyone within 30 metres.

Formula

Units per floor

per floor = maximum of the minimum and ceiling(floor area / coverage per unit)

Worked example

With the default values below, Fire Extinguisher Sizing Calculator returns Extinguishers required of 4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Floor area to protectminimum 1 m2: 200 m2
Hazard levelone of Light hazard (one 13A unit per 200 m2), Ordinary hazard (one per 200 m2, minimum two), High hazard (one per 100 m2): Ordinary hazard (one per 200 m2, minimum two)
Number of floorsminimum 1: 2

Results

Extinguishers required: 4
Extinguishers per floor: 2
Area covered by each unit: 200 m2
Maximum travel distance to an extinguisher: 30 m

Step by step

1Values used
2Units per floor
3Extinguishers required= 4
4Extinguishers per floor= 2
5Area covered by each unit= 200 m2
6Maximum travel distance to an extinguisher= 30 m

Assumptions and limits

The result is derived only from the 3 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 whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
General guidance only. Fire extinguisher provision must follow your local fire safety regulations and a competent risk assessment.

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

General guidance only. Fire extinguisher provision must follow your local fire safety regulations and a competent risk assessment.

Frequently Asked Questions

How is the Fire Extinguisher Sizing figure worked out?

per floor = maximum of the minimum and ceiling(floor area / coverage per unit). The usual rule provides one 13A rated unit per 200 square metres of light or ordinary hazard floor space, doubled for high hazard, with a minimum of two per floor and no more than 30 metres travel distance.

Why does this matter?

The travel distance limit often drives the count more than the area rule, because a long thin floor plan needs extra units to keep everyone within 30 metres.

What do I need to enter?

Enter floor area to protect, hazard level, number of floors. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.