How to split bills when living together
The best bill-splitting system is the one that feels fair and never needs a monthly argument. You only need three decisions: what counts as shared, how you split it (50/50 vs proportional vs custom), and how you’ll check it still works when things change.
Use the calculator to build a shared-cost split
Opens the main calculator prefilled so you can define shared costs, choose a split, and see the leftovers for both people.
No signup. Private. Links are shareable and can be reset anytime.
The 3-step framework
- Define shared costs: housing (mortgage), council tax, utilities, insurance, a maintenance buffer, and optionally groceries.
- Pick a split rule: 50/50, proportional by income, or a custom split like 60/40 or 66/33.
- Validate it: check leftovers and run stress tests (+1%, +2%, and one‑income).
This is budgeting guidance only — it’s not financial advice. The goal is clarity and resilience.
Worked examples (with numbers)
Example 1: proportional split for unequal incomes
Total shared cost: £2,890 / month
Proportional: A £1,861 · B £1,029 · 50/50: A £1,445 · B £1,445
Selected mode: proportional · Leftovers: A £1,939 / B £1,071
Example 2: custom split as a stable rule (60/40)
Total shared cost: £3,121 / month
Proportional: A £1,684 · B £1,437 · 50/50: A £1,560 · B £1,560
Selected mode: custom · Leftovers: A £1,528 / B £1,652
Stress test for peace of mind
A split can look fine until rates rise or one income drops. That’s why stress tests matter: they help you spot “works today, breaks later” situations. If the stress tests look risky, the fix is usually the house price or the buffer — not an argument about percentages.
FAQ
Do we have to split everything?
No. The calm approach is to define a shared list (housing + core bills) and keep personal spending personal. That keeps the rule clear and reduces arguments.
Should we split groceries?
Many couples do, but not always. If one person eats very differently or travels a lot for work, you might keep groceries separate or do a hybrid. The calculator lets you toggle groceries as shared.
Is a joint account necessary?
It’s optional. A joint account can make the system frictionless (each contributes their share, bills go out automatically), but it’s not required for a fair split.
How do we avoid resentment?
Make the goal explicit: balanced leftovers and resilience, not “who pays more”. Agree a review point and rerun the numbers when circumstances change.
Explore related UK guides
Related guides
Mortgage & bills split calculator
Run your numbers live and share a scenario link.
50/50 vs proportional vs custom splits
Choose a split that feels fair and stays sustainable.
Split the mortgage by income (UK)
Proportional splits explained with worked examples.
Proportional bills split calculator guide
Turn take-home pay into a clean monthly split.
66/33 vs 50/50 split for couples
When a custom split beats proportional (and when it doesn’t).
60/40 bills split guide
A simple compromise between 50/50 and proportional.
70/30 bills split guide
When a fixed split makes sense (and how to validate it).
75/25 bills split guide
For very different incomes: keep leftovers and resilience in view.
Should we split the mortgage 50/50?
A simple decision framework using leftovers and stress tests.
Partner earns more — what split is fair?
Proportional vs 50/50 vs custom, explained without judgement.
Tip: open a guide in one tab and the calculator in another to compare options quickly.