Partner earns more — what split is fair (mortgage + bills)?

When incomes are different, “fair” rarely means “same amount”. A fair split is one that keeps both people financially safe: reasonable leftovers each month, a savings rate that survives, and a plan that still works if rates rise or one income drops.

Last updated: 2025-12-17

Built by Brandon

Methodology

Use the calculator with a proportional split

Opens the main calculator prefilled so you can compare proportional vs 50/50 vs a custom split and see leftovers.

No signup. Private. Links are shareable and can be reset anytime.

Use the calculator with these defaults Open the calculator

Three fair ways to split costs

There isn’t one “correct” split. Most couples land on one of three approaches:

Proportional (by income): each person pays the same share of costs as their share of take‑home pay. This tends to balance leftovers.
50/50: simplest, and often fine when incomes are close and both people stay comfortable.
Custom: a stable rule like 60/40, 66/33, or 70/30, chosen to protect a savings goal or reflect other realities (childcare, deposit, risk).

The calculator is designed to make the outcome visible: who pays what, what each person has left, and whether the plan is resilient. Budgeting guidance only — not financial advice.

Worked examples (with numbers)

Example 1: proportional keeps leftovers balanced

Incomes: A £4,100 / B £2,100 · Home £420,000 · Deposit 12%

Total shared cost: £2,942 / month

Proportional

A £1,946 · B £997

50 / 50

A £1,471 · B £1,471

Selected mode: proportional · Leftovers: A £2,154 / B £1,103

Open this scenario in the calculator When 50/50 works (and when it doesn’t)

Example 2: custom split to protect a savings goal

Incomes: A £3,600 / B £2,400 · Home £500,000 · Deposit £90,000

Total shared cost: £3,468 / month

Proportional

A £2,081 · B £1,387

50 / 50

A £1,734 · B £1,734

Selected mode: custom · Leftovers: A £1,311 / B £1,221

Open this scenario in the calculator When 50/50 works (and when it doesn’t)

Stress test for reassurance

Even if a split feels fair today, couples usually want reassurance it’s resilient. Stress tests answer two high‑trust questions:

Rate rises: what happens to the monthly payment at +1% and +2%?
One income: could either person cover shared costs for a month or two if needed?

Read the stress test guide

FAQ

Is proportional the “right” answer?

It’s a strong default because it tends to balance leftovers, but it isn’t mandatory. Custom splits can be better if you’re protecting a savings goal, reflecting childcare, or accounting for deposit differences.

Should the higher earner cover 100% of bills?

Some couples do temporarily (e.g. during parental leave), but for most people it’s healthier to agree a split that both can sustain and that doesn’t create a dynamic of dependence or resentment.

What if the lower earner feels guilty paying less?

Use the maths to make the trade‑offs explicit. A fair split isn’t about paying the same amount; it’s about both people being able to live and save without chronic stress.

Do we need separate accounts?

Not necessarily. Many couples use a joint account for shared costs, with each person contributing their agreed amount. The important bit is the agreement, not the bank setup.