Split a shared water bill
One supply, one bill, several units. Enter the readings and this works out what each unit owes — and, just as usefully, how much water the main meter recorded that never reached anyone's tap.
The bill
The full amount, including any standing charge.
The part of the bill that does not depend on consumption, split evenly between units. Leave at zero to split everything by volume.
What the shared supply meter recorded over the same period, in m³.
The units
One row per apartment, house or connection, with the submeter readings at the start and end of the period.
| Unit | Previous (m³) | Current (m³) | Used (m³) | Share | Owes | Remove |
|---|---|---|---|---|---|---|
| 120 | 28.2% | €338.82 | ||||
| 95 | 22.4% | €268.24 | ||||
| 210 | 49.4% | €592.94 | ||||
| Total | 425 | €1,200.00 | ||||
Unaccounted water
- Main meter minus submeters
- 75 m³
- Share of the main meter
- 15%
- What it costs the community
- €180.00
A gap this large is not measurement error. Common causes are a leak on the shared pipework, an unmetered connection, or a submeter that has stopped counting.
How the split works
Each unit's consumption is its current reading minus its previous one. The standing charge, if you set one, is divided equally between units; whatever is left of the bill is divided in proportion to consumption. The unaccounted figure is the main meter minus the sum of the submeters, valued at the bill's own effective rate.
An estimate to check a split or prepare a discussion, not a legal apportionment — your building's own rules decide how costs are allocated. Nothing you type here leaves your browser.
Doing this by hand every quarter?
The readings are the hard part, not the arithmetic. Remote-read meters report on their own, so the split is ready when the bill arrives and the unaccounted figure is tracked continuously rather than discovered afterwards.
Common questions
- Why do the submeters never add up to the main meter?
- Some gap is expected. Submeters have a tolerance and under-read very low flows, communal taps and irrigation are often unmetered, and readings are rarely taken at exactly the same moment. A few per cent is ordinary. Ten per cent or more usually points at something specific — a leak on shared pipework, an unmetered connection, or a stopped meter.
- Should the standing charge be split equally or by consumption?
- That is a decision for the building, not a technical one. Splitting the fixed part equally reflects that every unit benefits from the connection whether or not it uses water; splitting everything by volume is simpler to explain. This tool supports both — set the standing charge to zero for a pure volume split.
- One unit was empty all quarter. Is a zero share correct?
- For the consumption part, yes — no water used means no variable cost. The standing charge still applies if you are splitting one equally, which is usually the argument for having one.
- What if a submeter reads lower than last time?
- A mechanical or static meter does not count backwards, so a lower reading is a transcription error, a meter that has been replaced, or a rollover on a meter with too few digits. The calculator flags the row and treats it as zero rather than handing every other unit a distorted share.