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Income-Proportional Bill Split Calculator

Split shared expenses fairly by income, not headcount.

How it is calculated

Each person pays in proportion to their income: share_n = bill_total × income_n ÷ (income1 + income2 + income3). All three incomes and the bill must be entered; for a two-person split, put 0 in the third income field and that person's share is $0.00. Incomes can be monthly or yearly as long as everyone uses the same period, because only the ratio counts. The bill is a money amount for whatever period you are splitting. Only the first person's percentage is displayed (income1 ÷ total income × 100); the other percentages follow from the same ratio. If every income is zero or any value is negative, there is no result. Use net (take-home) or gross income consistently for all.

Worked example

Three housemates share a $1,600 monthly bill. Incomes: $4,200, $2,800 and $1,000, which total $8,000. Person 1 earns 4,200 ÷ 8,000 = 52.50% of the total, so pays 1,600 × 0.525 = $840.00. Person 2 pays 1,600 × 2,800 ÷ 8,000 = $560.00 and person 3 pays 1,600 × 1,000 ÷ 8,000 = $200.00.

The three shares add up to $1,600.

Try this example →

Common mistakes

  • Mixing income periods, such as one monthly salary and one yearly salary. The shares are then badly skewed; use the same period for everyone.
  • Mixing gross and net income. If one person enters pre-tax pay and another take-home pay, the split is unfair; pick one basis for all.
  • Leaving the third income blank for a two-person split. The field must contain 0, otherwise there is no result.
  • Entering the bill per person instead of the full shared total. The tool divides the amount you enter, so it must be the whole bill.
  • Reading the single percentage as a share for everyone. It is only person 1's share of the combined income.

About this calculator

An income-proportional split divides a shared bill so that each person pays in proportion to their own income, rather than splitting it evenly by headcount. If one partner earns 70% of a household's combined income, they pay 70% of the shared bill instead of an automatic 50%, so the expense takes up roughly the same share of each person's budget regardless of how unequal their incomes are.

The calculation is straightforward: each person's income is divided by the total combined income of everyone splitting the bill to get their percentage share, and that percentage is then applied to the total bill amount — this calculator supports up to three people splitting together.

Couples and roommates with unequal incomes commonly use proportional splitting for rent, utilities, and groceries, since a strict 50/50 split can feel disproportionately burdensome to the lower earner, while a proportional split is widely seen as a fairer way to share costs without either person tracking every individual expense.

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