How to Split Charges in a Flatshare: Calculation Methods

Electricity, water, internet, cleaning of common areas: charges are often the first source of tension in a flatshare. Not because of the amounts — they are rarely huge — but because everyone has their own idea of what would be "fair". Several splitting methods exist, and none is objectively the best.

Equal Split (Per Head)

The total charges are divided by the number of flatmates. It is the simplest method to understand and apply: everyone pays the same amount.

Its limit shows up when rooms or usage differ significantly — a large room with a balcony versus a small windowless room, or a flatmate who is away half the month. Simplicity then comes at the cost of a sense of unfairness.

Split Pro Rata to Room Size

Each flatmate pays a share proportional to their room's floor area relative to the total floor area. A 20 m² room out of a 60 m² total represents a third of the charges.

This is noticeably fairer when room sizes vary a lot. In return, you need to measure the surfaces once and for all, and agree on how shared spaces are treated.

Mixed Split

This is often the best compromise in practice: not every charge is treated the same way.

Fixed charges — internet, upkeep of common areas, subscriptions — are split per head: they depend on neither room size nor actual consumption. Variable charges — water, electricity, heating — are split pro rata to room size, or by actual usage where separate meters exist.

Why the Calculation Should Be Automatic, Not Done by Hand

A shared spreadsheet works really well... for the first three months. Then someone edits a formula, a column shifts, and above all: a flatmate leaves and another moves in. Everything then needs recalculating, and that is when errors creep in without anyone noticing.

A living agreement recalculates shares with every move-in and move-out, while keeping the one thing that matters: the sum of the shares always equals the total. No manual recalculation, no outdated version lying around, no argument over who owed what back in March.

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