Income-based split calculator

When to split a bill by income

Use it when the people sharing a bill earn very different amounts and an equal split would take a bigger bite out of one person’s pay than another’s. It works for one bill such as rent or a shared utility, and for a household’s whole set of shared bills. For the reasoning behind it, see how to split bills based on income.

How the calculator works

Enter the bill and up to six incomes. A person left at 0 is not counted.

1. Add the incomes together.
2. Each person’s percent is their income divided by that total.
3. Each person’s share is the bill times that percent.
4. For comparison, an equal share is the bill divided by the number of people.

The unit does not matter as long as it is the same for everyone. Incomes of $3,000 and $5,000 a month give the same split as $36,000 and $60,000 a year, because only the proportions count.

Worked example: an $1,800 bill and two incomes

Say two people split an $1,800 bill and earn $3,000 and $5,000 a month. These are the numbers the calculator opens with.

• Total income: $3,000 + $5,000 = $8,000.
• Person 1: $3,000 ÷ $8,000 = 37.5%, so $1,800 × 37.5% = $675.
• Person 2: $5,000 ÷ $8,000 = 62.5%, so $1,800 × 62.5% = $1,125.
• Equal split: $1,800 ÷ 2 = $900 each.

Person 1 pays $225 less than an equal split and Person 2 pays $225 more. Both put the same 22.5% of their own income toward the bill: $675 ÷ $3,000 and $1,125 ÷ $5,000 are each 0.225, and so is $1,800 ÷ $8,000. That is what makes it a proportional split, also called pro rata, and the calculator shows it as the share of income each person puts toward the bill.

A three-person example

Say three people split a $960 bill and earn $2,000, $3,000 and $3,000 a month. The total is $8,000, so the percents are 25%, 37.5% and 37.5%.

Person	Share of the total	Pays	Against an equal $320
Person 1 ($2,000)	25%	$240	$80 less
Person 2 ($3,000)	37.5%	$360	$40 more
Person 3 ($3,000)	37.5%	$360	$40 more

The shares add up to $960. The amount one person saves is the amount the others add, so the differences net to zero, give or take a cent of rounding.

When the cents do not divide evenly

Three equal incomes on a $1,000 bill give $333.333 each, and a bill has no thirds of a cent. The calculator gives $333.34, $333.33 and $333.33, which add up to $1,000. With unequal incomes, rounding each share by hand can leave the total a cent or two off. The calculator gives the spare cent to the share that lost the most in rounding.

Mistakes to avoid

• Mixing periods. A monthly figure next to a yearly one makes the yearly person count twelve times as much as they should.
• Mixing kinds of income. Use before-tax figures for everyone or take-home figures for everyone.
• Leaving a non-paying person in. Set their income to 0 so they are not counted.
• Applying it to every bill without agreeing first. Some households split rent by income and groceries equally. Decide which bills use the income split before you start.

Recording the shares in EvenOut

To keep the split on record, add the bill as an expense in EvenOut, choose “Exact amounts” and type each dollar share. The pill reads “All assigned” when the amounts add up to the total. If your percents come out round, such as 25 and 75, “Percent” works as well. For a fixed monthly bill like rent, set “Repeat” to “Monthly” and the same split is added each month.

If you would rather set the percents yourself by agreement, the percentage split calculator takes them directly, and the formulas for splitting bills lays out each method side by side.