Household Water Usage Calculator
Add up what your home actually uses — showers, flushes, washing, everything else — in litres a day and money a month.
Results
What this tool does
A water bill arrives as a single number every few months, long after you could do anything about it. This page takes it apart. Count the showers and how long they last, the flushes, the washing machine loads, and a figure for everything else, and it returns litres a day, cubic metres a month and what that costs. The share that is showers is shown separately, because in most homes that one line is where the bill actually comes from.
Formula
litres per day = showers + flushes + laundry + rest · each part counted separately and added up
Variables
| Symbol | Meaning | Unit |
|---|---|---|
p | People in the house | — |
sw | Showers per person per week | — |
sm | Minutes in the shower | min |
sf | Shower flow rate | L/min |
fd | Flushes per person per day | — |
cl | Litres per flush | L |
ww | Washing machine loads a week | — |
lw | Litres per load | L |
ot | Everything else, per day | L |
pr | Water price | — |
L | Litres a day | L |
PP | Litres per person per day | L |
M | Cubic metres a month | m³ |
C | Cost | — |
Y | Total cost per year | — |
S | Share that is showers | % |
Worked example
- People in the house3
- Showers per person per week7
- Minutes in the shower8 min
- Shower flow rate9 L/min
- Flushes per person per day5
- Litres per flush6 L
- Washing machine loads a week4
- Litres per load50 L
- Everything else, per day30 L
- Water price2.2
- Litres a day365 L
- Litres per person per day122 L
- Cubic metres a month11.10 m³
- Cost24.41
- Total cost per year292.95
- Share that is showers59.2 %
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
Frequently asked questions
How do I find my shower's flow rate?
Put a bucket under it, run it flat out for exactly fifteen seconds, and measure what you caught. Multiply by four and you have litres per minute. It is worth doing rather than guessing: an old shower head can be three times the flow of a modern one, and this single number usually decides more than half the total on this page.
Why does the month use 30.44 days?
Because a year of 365.25 days divided by twelve is 30.4375, and that is what an average month actually is. Using thirty would quietly lose you five days a year, which on a water bill is real money. The yearly figure here uses 365.25 for the same reason.