HOW IT WORKS
How to calculate a metered water bill
A metered water bill is usually built from two parts: charges linked to the amount of water used and fixed charges that apply regardless of usage. This calculator keeps those parts separate so you can see what is driving the estimate.
Where to find the figures on your water bill
Use the tariff or charges section of your latest statement, or your water company's current charges page. Look for the clean-water volumetric rate, wastewater or sewerage volumetric rate, fixed or standing charges, and any separately listed surface water drainage charge. If a rate is shown as pounds per cubic metre, multiply it by 100 before entering it in a field labelled p/m³; for example, £1.85/m³ is 185p/m³.
The pre-filled values in the calculator are illustrative examples only. They are not a UK average and should be replaced with your own supplier's figures for a meaningful bill estimate.
Water meter units: cubic metres and litres
Water meters commonly record usage in cubic metres. One cubic metre (1 m³) equals 1,000 litres, so 6,000 litres is 6 m³. With the tariff currently entered above, the combined variable water and wastewater charge is £3.31 per m³ (0.331p per litre), before fixed and drainage charges.
On the same entered rates, 6,000 litres would have a variable water-and-wastewater cost of £19.86, before standing charges and any surface water charge.
What this calculator includes
- Annual metered usage entered in m³ or litres
- Separate clean-water and wastewater unit rates
- Standing charges entered as annual pounds or daily pence
- An optional annual surface water drainage charge
- Annual, monthly, weekly and daily bill estimates
- Variable cost per cubic metre, per 1,000 litres and per litre
What this calculator does not model
It does not calculate an unmetered bill based on rateable value, identify a water supplier from a postcode, or automatically apply company-specific return-to-sewer percentages, discounts, allowances or special tariffs. Household charging also differs across the UK; use the charging method and tariff that applies to your property.
Why your actual water bill may be different
Water and sewerage pricing varies by supplier, location and tariff period. Companies can also apply different wastewater assumptions, drainage arrangements, meter-related fixed charges and adjustments. Treat the result as a planning and bill-checking estimate rather than a replacement for your supplier's statement.
Methodology and sources
The calculation follows the basic structure used for metered charging: a volumetric charge based on water used plus fixed charges, with wastewater and drainage handled separately where applicable. Methodology reviewed 7 August 2026.