Shower Flow Rate Calculator

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

About Shower Flow Rate Calculator

The bucket test measures shower flow directly: litres collected divided by seconds, scaled to a minute. From there the water and energy cost of a shower follows immediately. Low-flow heads deliver 6-9 L/min while an unrestricted mixer can exceed 15 L/min.

Formulas

Flow rate

L/min = litres collected x 60 / seconds; GPM = L/min / 3.785

Per shower

Litres = flow L/min x shower minutes

Worked example

With the default values below, Shower Flow Rate Calculator returns Shower flow rate of 16.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Water collectedminimum 0.1 L: 8 L
Collection timeminimum 1 s: 30 s
Typical shower lengthminimum 0.5 min: 8 min

Results

Shower flow rate: 16.00 L/min
Flow in US gallons: 4.23 GPM
Water per shower: 128.0 L
Annual use, one shower a day: 46,720 L

Step by step

1Values used
2Flow rate
3Per shower
4Shower flow rate= 16.00 L/min
5Flow in US gallons= 4.23 GPM
6Water per shower= 128.0 L
7Annual use, one shower a day= 46,720 L

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.

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

Frequently Asked Questions

How is the Shower Flow Rate figure worked out?

L/min = litres collected x 60 / seconds; GPM = L/min / 3.785. The bucket test measures shower flow directly: litres collected divided by seconds, scaled to a minute.

Will a low-flow head feel weaker?

Not necessarily. Aerating and laminar heads maintain perceived pressure by increasing exit velocity, so the reduction is mostly invisible below about 8 L/min.

What values do I need to enter?

This calculator takes 3 inputs: Water collected, Collection time, Typical shower length. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.