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Split expenses by income: the proportional split calculator
When one partner earns more, splitting everything 50/50 weighs heavier on the one who earns less. A proportional split shares common costs according to each income. Enter your numbers: the calculator does the math and compares it with 50/50 and a mixed approach.
In short
- In a proportional split, each partner pays a share of the shared costs equal to their share of the household income.
- Formula: A’s share = A’s income ÷ (A’s income + B’s income).
- Example: with $1,500 and $2,000 of take-home pay, A pays 43% and B 57%; on $1,400 of shared costs, that is $600 and $800.
- With a proportional split, both partners spend the same percentage of their income on the household (40% here); with 50/50, the lower earner spends a bigger share.
Work out your split
Enter each partner’s monthly take-home pay, then your shared costs, separating fixed costs (rent or mortgage, utilities, insurance, internet) from everyday spending (groceries, outings, gas). The table compares three methods and shows what each of you has left once your share is paid.
Split by income calculator
Person A share
43%
$600 a month
Person B share
57%
$800 a month
| Method | A pays | B pays | A has left | B has left |
|---|---|---|---|---|
| 50/50 | $700 | $700 | $800 | $1,300 |
| Proportional to income | $600 | $800 | $900 | $1,200 |
| Mixed (fixed costs by income, everyday 50/50) | $635.71 | $764.29 | $864.29 | $1,235.71 |
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The proportional split formula
The idea fits in one line: each partner contributes according to what they earn. Add both incomes, work out each person’s share of the total, then apply that percentage to the shared costs.
A’s share = A’s income ÷ (A’s income + B’s income)
B’s share = B’s income ÷ (A’s income + B’s income)
Amount paid by A = shared costs × A’s share
Use take-home pay, what actually lands in the account, not gross salary. If one of you has irregular income (freelance, bonuses, overtime), use an average over several months and redo the math when things change.
Worked example: $1,500 and $2,000
Alex takes home $1,500 a month and Sam $2,000, so $3,500 together. Their shared costs come to $1,400: $900 of fixed costs and $500 of groceries and outings.
- Alex’s share: 1,500 ÷ 3,500 = 0.4286, so 43%.
- Sam’s share: 2,000 ÷ 3,500 = 0.5714, so 57%.
- Alex pays 1,400 × 0.4286 = $600, Sam pays 1,400 × 0.5714 = $800.
What each partner has left, by method
50/50
- Alex pays
- $700
- Sam pays
- $700
- Alex has left
- $800
- Sam has left
- $1,300
Proportional to income
- Alex pays
- $600
- Sam pays
- $800
- Alex has left
- $900
- Sam has left
- $1,200
Mixed (fixed by income, everyday 50/50)
- Alex pays
- $635.71
- Sam pays
- $764.29
- Alex has left
- $864.29
- Sam has left
- $1,235.71
| Method | Alex pays | Sam pays | Alex has left | Sam has left |
|---|---|---|---|---|
| 50/50 | $700 | $700 | $800 | $1,300 |
| Proportional to income | $600 | $800 | $900 | $1,200 |
| Mixed (fixed by income, everyday 50/50) | $635.71 | $764.29 | $864.29 | $1,235.71 |
With 50/50, Alex spends 47% of their income on the household and Sam 35%. With a proportional split, both spend 40%. That is the whole point: the effort is the same for both, even though the amounts differ.
50/50, proportional or mixed: which one?
- 50/50 is the simplest. It works well when your incomes are close, or when you mostly share small expenses.
- Proportional is the fairest when there is a clear income gap. It keeps one partner from running short while the other saves.
- Mixed is a middle ground: big fixed costs by income, everyday spending half and half.
There is no universal right answer: the best method is the one you both find fair. For a full comparison, read How couples split expenses.
Making a proportional split work every month
The math is easy once. The hard part is sticking to it when bills are paid sometimes by one partner, sometimes by the other. Two options:
- A monthly transfer from each partner into a joint account, in proportion to income. Simple, but you need a joint account and must adjust amounts when costs change.
- A shared expenses app: each partner logs what they pay, and the app works out who owes whom based on your split.
In SAVY, every expense records who paid and who it is shared between, and the app keeps your couple balance up to date. On the free plan, expenses are split equally. Custom splits (60/40, shares or exact amounts, even on the rent) are part of SAVY Plus.
Frequently asked questions
How do you split expenses by income as a couple?
Divide each partner’s take-home pay by your combined income. With $1,500 and $2,000, the first partner’s share is 1,500 ÷ 3,500 = 43% and the second’s 57%. Apply those percentages to your shared costs.
Should we use gross or net income?
Net, meaning what actually lands in your account each month. If income varies, use an average over several months.
Is a proportional split fairer than 50/50?
When incomes differ, yes: both partners spend the same percentage of their income on the household. When incomes are close, 50/50 gives almost the same result and is simpler.
Can I split proportionally in SAVY?
Yes, with SAVY Plus: custom splits let you share an expense by percentage, for example 43/57, by shares or by exact amounts. The free plan splits each expense equally.