How to use the income based bill split calculator
- Add each person with a monthly income, using the figure you want the split to be based on.
- List the shared bills: name and monthly amount, separated by a comma.
- Choose how to split: in proportion to income, so everyone pays the same percent of income, or so everyone has the same amount left over.
- Read who pays what, the share of bills and of income, and the amount left, then read the statement table for each bill.
Formula
proportional: contribution = bills x income / total income
equal money left: contribution = income - L, where L = (total income - bills) / people
if a low earner would pay less than 0, that person pays 0 and L is found again among the others
amounts are rounded to cents with the largest remainder method so they add up to the bills
The percentage of income paid is the same for everyone in the first method. In the second, the amount left after bills is the same for everyone who pays anything.
Three people sharing $2,925.50 of bills
Alex earns $4,800, Sam $3,200 and Jo $1,500 a month, a combined $9,500, and the bills are rent $2,100, electric $120.50, internet $65 and groceries $640. In proportion to income everyone pays 30.79% of income: Alex $1,478.15, Sam $985.43 and Jo $461.92, which add up to $2,925.50.
To leave everyone the same amount, the common leftover would be (9,500 - 2,925.50) / 3 = $2,191.50, which is more than Jo earns. So Jo pays nothing and the others share the bills: the leftover becomes $2,537.25, Alex pays $2,262.75 and Sam pays $662.75, and Jo keeps $1,500.
Two ideas of fairness
Splitting in proportion to income treats a bill as a share of what each person earns. Splitting for equal money left treats the bill as something the household must cover so that nobody ends up with less spending money than anyone else. The second can ask more from higher earners and can leave a low earner out of the bills altogether.
Neither is the right answer for every household. Agree on a method together, and consider needs that a spreadsheet cannot see, such as who uses which room or who has extra costs.
Cents and statements
Each person’s contribution is rounded to the cent so that the total equals the bills exactly. The statement table splits every bill in the same proportions and rounds each bill on its own, so a person’s statement total can differ from the amount in the first table by a few cents.
To split rent by room size use the Rent Split Calculator, to split a restaurant bill by item try the Itemized Bill Splitter, and to plan yearly costs see the Annual Bills Monthly Set-Aside Planner.
Assumptions and limits
- Incomes are monthly amounts in one currency and are treated as the money available to share bills.
- Between 2 and 8 people and up to 40 bills are read. At least one income must be above zero.
- The bills cannot be more than the combined income.
- Taxes, savings, debts and differing needs are not modeled.
- Nothing typed here leaves your browser.
Frequently asked questions
Why does someone pay nothing in the equal leftover method?
If the common leftover is more than a person’s income, equalizing would require paying them money. The page instead sets that person’s share to zero and spreads the bills across the others.
Should I use gross or net income?
Use whichever you agree on, but use the same kind for everyone. Net income, the amount that reaches each person after tax, is closer to what is available to spend.
Can I include a person with no income?
Yes. In proportional mode they pay nothing, and in equal leftover mode they also pay nothing, with the others covering the bills.
Why do the statement totals differ by cents?
Each bill is rounded on its own to the cent. The totals in the first table are rounded once, over all the bills, so they can differ from the statement by a few cents.