Split a mortgage when incomes are unequal (UK)
When incomes are different, “fair” usually means sustainable for both people. This page shows how to use proportional splits (by take‑home pay) and compare them against 50/50 and a simple custom split, using realistic UK numbers.
Prefer to start from the hub? Open the main calculator.
Calculator
Worked examples
Each example uses the same calculator engine. Use “Open in calculator” to share or compare scenarios.
Unequal incomes, proportional split (baseline)
Incomes: A £3,800 · B £1,600
Shared total: £2,570 / month
Split (proportional): A £1,809 · B £762 · Leftovers: A £1,991 · B £839
Same home, test a custom 66/34 split
Incomes: A £3,800 · B £1,600
Shared total: £2,570 / month
Split (custom): A £1,696 · B £874 · Leftovers: A £2,104 · B £726
FAQ
Is proportional always the best split?
It’s a strong default because it tends to balance leftovers. But couples often choose a custom split if it’s simpler to maintain, or if the deposit and other costs aren’t evenly shared.
What if one person can’t afford their share under 50/50?
That’s a signal the house price (or total shared costs) may be too high for your joint plan. Try proportional, reduce the purchase price, increase the deposit, or build a bigger emergency buffer.
Should we include groceries in the shared total?
If you’re using this to judge affordability, including groceries can make the leftover more realistic. If you keep personal spending separate, toggle groceries off and compare again.
Related links
- Open the main calculator (hub)
- Fair splits: proportional vs 50/50 vs custom
- How it works (formulas and methodology)
- Stress test: rate rises + one-income
- Split mortgage by income (UK)
- 66/33 vs 50/50 split (UK)
- Proportional bills split (UK)
- How much house can we afford? (UK)
- Stamp Duty calculator for couples (UK)
- FAQ (assumptions and common questions)
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).
Stamp Duty (SDLT) calculator for couples
Standard vs first-time buyer relief + surcharges.
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.
Tip: open a guide in one tab and the calculator in another to compare options quickly.