Split by Income
When incomes differ, a 50/50 split isn't neutral — it just moves the unfairness to the smaller paycheck. Split proportionally instead: same percentage of income for everyone, both options shown honestly.
| Pays | % of income | If split equally | |
|---|---|---|---|
| Person A | $1,250 | 25.0% | $1,000 (20.0%) |
| Person B | $750 | 25.0% | $1,000 (33.3%) |
Both columns are fair by a different definition — this tool shows the numbers, the conversation is yours.
Spotted a mistake or have an idea? — errors get fixed and credited publicly.
Last reviewed: July 20, 2026 · Formulas verified by automated tests before every release.
How do you split expenses proportionally to income?
Each person's share = their income ÷ combined income × the expense. With monthly incomes of $5,000 and $3,000 sharing $2,000 rent, the proportional split is $1,250 and $750 — both pay 25% of their income. An equal split would take 20% from one and 33% from the other, which is the quiet asymmetry this calculator makes visible.
The formula and the worked example
share = income ÷ total income × expense · check: everyone's share ÷ their income = the same %
The check line is the whole philosophy: after a proportional split, the "% of income" column is identical for everyone — equal sacrifice, unequal amounts. The comparison column shows what 50/50 would do to each person, because a fair conversation needs both numbers on the table, not just the one that flatters an argument.
The conversation, honestly
Money splits end more relationships than money amounts do, and the failure mode is usually silence: one default (often 50/50) chosen by inertia, resentment compounding monthly like interest. This page is built to be sent before the talk — neutral numbers, both definitions of fair, no verdict. Some couples land on proportional, some on equal, some on "proportional for rent, equal for pizza" — all workable, if chosen out loud. What doesn't work is never running the numbers.
Sources, assumptions and limitations
- Formula: share = income ÷ Σ incomes × expense; equal-split comparison = expense ÷ people
- Assumptions: Incomes and the expense are for the same period (monthly works best) and the same basis for everyone (net recommended); up to five people.
- Not included: Assets, debts, childcare and non-monetary contributions — real fairness talks include more than income. This tool feeds the conversation; it doesn't settle it. Incomes never leave the browser and are excluded from links by our data-sensitivity policy.
- Last reviewed: July 23, 2026 by the CalcNotebook team
Frequently asked questions
How do we split rent based on income?
Each person pays the same percentage of their income: share = your income ÷ combined income × the expense. Incomes of $5,000 and $3,000 splitting $2,000 rent give $1,250 and $750 — both are paying exactly 25% of what they earn.
Is proportional splitting fairer than 50/50?
They are fair by different definitions: 50/50 equalizes the amounts, proportional equalizes the sacrifice. On unequal incomes, an equal split can quietly cost the lower earner twice the share of their income — the table shows both side by side so the choice is informed, not accidental.
Which income should we enter — gross or net?
Net (take-home) reflects what each person actually has to spend, so it usually feels fairer. Whichever you choose, use the same basis for everyone.
Where do the incomes we type go?
Nowhere. They are processed in your browser, never uploaded or stored, and this tool deliberately has no "link with my numbers" — income figures should not live in URLs, even convenient ones. Share the result as text if you both want a copy.