Show the formula and working
This free water usage calculator adds up how many litres your household uses each day for showers, baths, toilets, appliances, taps and the garden, for homes in the UK, Ireland and Europe. It shows each activity’s share, the litres per person compared with the average, and the yearly cost on a water meter.
Quick answer: A water usage calculator multiplies each activity by its litres and adds them up. Two people with two 8 minute showers a day at 9 litres a minute, one bath a week, ten flushes and normal appliance use come to about 308 litres a day, or 154 litres each, against the England average of 140.
What Is a Water Usage Calculator?
A water usage calculator is a tool that estimates a household’s daily and yearly water use by adding up the litres used by each activity, and converts the total into a cost.
The formula in plain words: showers use flow rate times minutes times the number of showers, taps use flow rate times minutes, toilets use flushes times litres per flush, and weekly items such as baths and washing are divided by 7 to give a daily figure. Add them up for litres a day, divide by the number of people for litres per person, and multiply by 365 and by the price per cubic metre for the yearly cost.
How Do You Use the Water Usage Calculator?
- Enter the People in the home.
- Enter the Showers per day (household), Minutes per shower and Shower flow rate, then the Baths per week (household) and Litres per bath.
- Enter the Toilet flushes per day (household) and Litres per flush.
- Enter the Washing machine loads per week, Litres per wash, Dishwasher loads per week and Litres per dishwasher load from the energy labels.
- Enter the Tap running minutes per day (household), the Tap flow rate, any Garden and car litres per week, and your Water and sewerage price per m³.
- Read the litres per day, per person and the yearly cost, then open “Show the formula and working” to see where the water goes.
How Much Water Does the Average Person Use?
The average person uses about 140 litres a day in England, 150 in Scotland and 145 in Northern Ireland, according to Waterwise. New homes in England are designed for no more than 125 litres per person per day under Approved Document G, or 110 litres where a planning condition requires the tighter optional figure. Showers, toilets and taps are usually the biggest uses.
How Much Water Does a Shower or Bath Use?
A bath typically uses around 80 litres, while a shower uses its flow rate times the minutes, so an 8 minute shower at 9 litres a minute uses 72 litres. A short shower can use a third of a bath, but a long power shower can use more than a bath. Time how long your shower takes to fill a 10 litre bucket to find its real flow; the electric shower cost calculator then adds the heating cost.
How Much Does Water Cost per Cubic Metre?
On a water meter you pay a price per cubic metre (1,000 litres) for clean water and usually another for sewerage, plus standing charges. Prices differ by water company and change each April, so the calculator uses an editable example of 4.00 per m³ for water and sewerage together. Add up the two volume rates on your own bill for an accurate figure. Without a meter, your bill does not change with use, though saving hot water still cuts energy costs.
How Can You Reduce Household Water Use?
Shorter showers make the biggest difference in most homes: cutting two showers a day from 8 to 4 minutes saves 72 litres a day at 9 litres a minute. Turning off the tap while brushing saves about 6 litres a minute, a dual flush toilet uses 4 to 6 litres against up to 13 for an old one, and full loads in the washing machine and dishwasher save water per item.
Typical Water Use by Activity
Figures from Waterwise unless marked as an example.
| Activity | Typical water use |
|---|---|
| Bath | Around 80 litres |
| Short shower | About a third of a bath |
| Power shower | Can use more than a bath |
| Dual flush toilet | 4 to 6 litres a flush |
| Older toilet | Up to 13 litres a flush |
| Running tap | About 6 litres a minute |
| Washing machine | Under 7.5 litres per kg of laundry for efficient models |
| Garden sprinkler | About 1,000 litres an hour |
Worked Example: A Two-Person Home
Example: two people, two 8 minute showers a day at 9 litres a minute, one 80 litre bath a week, ten 6 litre flushes a day, four 50 litre washes and three 10 litre dishwasher loads a week, 10 minutes of tap use a day at 6 litres a minute, and an example price of 4.00 per m³. These are the default inputs.
- Showers: 2 x 8 x 9 = 144 litres a day (47%).
- Toilet: 10 x 6 = 60 litres; taps: 10 x 6 = 60 litres.
- Washing machine 29, bath 11 and dishwasher 4 litres a day.
- Total: 308 litres a day, 154 litres per person.
- Per year: 308 x 365 / 1,000 = 112.5 m³, which costs £450.10 at the example price.
With the currency switch on euros, the same example price shows €450.10; enter your own local rate. To convert litres into gallons for older appliances, use the litres to gallons converter.
Water Usage Calculator FAQs
How much water does a family of four use per day?
At the England average of 140 litres per person, a family of four uses about 560 litres a day, or about 204 cubic metres a year. Your figure depends mostly on shower length and flow, so enter your own habits above.
How do I find my shower’s flow rate?
Hold a bucket marked at 10 litres under the shower at your usual setting and time how long it takes to fill. Divide 10 by the seconds and multiply by 60 for litres per minute. 60 seconds means 10 litres a minute.
Will a water meter save me money?
A meter usually saves money for homes that use less water than their rateable value assumes, often smaller households in larger homes. Work out your yearly cubic metres here, multiply by your company’s metered rates and compare with your current bill.
How much water does a washing machine use?
Waterwise says efficient washing machines use under 7.5 litres per kg of laundry. The energy label on newer machines shows the litres per cycle for the eco programme, which is the figure to enter in Litres per wash.
How much water does a dripping tap waste?
It depends on the drip rate, but a steady drip adds up to many litres a week, and a tap left running uses about 6 litres a minute. Fix dripping taps by replacing the washer or cartridge, and report leaks on the supply pipe to your water company.
What is 1 cubic metre of water in litres?
One cubic metre is exactly 1,000 litres, which is the unit water meters and bills use. A household using 308 litres a day uses about 9.4 cubic metres a month.
For more home running costs, see the home calculators.
Checked October 2026. Sources: Save water (Waterwise), Approved Document G (GOV.UK).