Sprinkler Density Requirement Calculator

Work out sprinkler density requirement instantly with clear inputs, formula shown and shareable results.

About Sprinkler Density Requirement Calculator

Sprinkler design density is the depth of water per minute the system must deliver over the assumed area of operation, set by hazard class: 2.25 mm/min for light hazard up to 10 mm/min or more for high hazard storage. Because one millimetre per minute over one square metre is one litre per minute, flow follows directly, and multiplying by the required duration gives storage.

Formulas

Design flow

L/min = design density mm/min x area of operation m²

Storage

m³ = flow L/min x duration min / 1000

Worked example

With the default values below, Sprinkler Density Requirement Calculator returns Design flow required of 1,080. Change any input above and every figure here is recalculated in your browser.

Inputs used

Hazard classificationone of Light hazard — 2.25 mm/min, Ordinary hazard group 1 — 5.0 mm/min, Ordinary hazard group 3 — 5.0 mm/min, High hazard — 10.0 mm/min: Ordinary hazard group 3 — 5.0 mm/min
Assumed area of operationminimum 1 m²: 216 m²
Required durationminimum 1 min: 60 min

Results

Design flow required: 1,080 L/min
Design density: 5.00 mm/min
Water storage required: 64.80 m³
Design flow: 18.00 L/s

Step by step

1Values used
2Design flow
3Storage
4Design flow required= 1,080 L/min
5Design density= 5.00 mm/min
6Water storage required= 64.80 m³
7Design flow= 18.00 L/s

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 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Sprinkler system design must be carried out by a qualified fire protection engineer to the applicable standard with full hydraulic calculation.

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

Preliminary estimate only. Sprinkler system design must be carried out by a qualified fire protection engineer to the applicable standard with full hydraulic calculation.

Frequently Asked Questions

How is the Sprinkler Density Requirement figure worked out?

L/min = design density mm/min x area of operation m². Sprinkler design density is the depth of water per minute the system must deliver over the assumed area of operation, set by hazard class: 2.25 mm/min for light hazard up to 10 mm/min or more for high hazard storage.

Why does the area of operation differ by hazard?

It reflects how far a fire is expected to spread before sprinklers control it. Higher hazard occupancies assume a larger area of simultaneous operation as well as a higher density.

What values do I need to enter?

This calculator takes 3 inputs: Hazard classification, Assumed area of operation, Required duration. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.