Sprinkler System Flow Calculator

Work out sprinkler system flow instantly with clear inputs, formula shown and shareable results.

About Sprinkler System Flow Calculator

Sprinkler system demand is design density multiplied by the assumed area of operation, since one millimetre per minute over one square metre is one litre per minute. Individual sprinkler discharge follows the orifice relation q = K sqrt(p), so dividing total flow by sprinkler discharge shows how many heads the design implies.

Formulas

System flow

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

Sprinkler discharge

q = K x sqrt(pressure in bar)

Worked example

With the default values below, Sprinkler System Flow Calculator returns Total system flow of 700.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Design densityminimum 0.5 mm/min: 5 mm/min
Assumed area of operationminimum 1 m²: 140 m²
Sprinkler K factorminimum 10: 80
Pressure at the sprinklerminimum 0.1 bar: 1 bar

Results

Total system flow: 700.0 L/min
Total system flow: 11.667 L/s
Flow per sprinkler: 80.00 L/min
Sprinklers assumed operating: 9

Step by step

1Values used
2System flow
3Sprinkler discharge
4Total system flow= 700.0 L/min
5Total system flow= 11.667 L/s
6Flow per sprinkler= 80.00 L/min
7Sprinklers assumed operating= 9

Assumptions and limits

The result is derived only from the 4 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 3 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 and hydraulically calculated node by node.

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 and hydraulically calculated node by node.

Frequently Asked Questions

How is the Sprinkler System Flow figure worked out?

L/min = design density mm/min x area of operation m². Sprinkler system demand is design density multiplied by the assumed area of operation, since one millimetre per minute over one square metre is one litre per minute.

Why an assumed area of operation?

Not every sprinkler in a building operates in a fire. Standards define a design area, typically 72-260 square metres by hazard class, that the water supply must cover simultaneously.

What values do I need to enter?

This calculator takes 4 inputs: Design density, Assumed area of operation, Sprinkler K factor, Pressure at the sprinkler. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.