Three worked examples
Each case below splits the same $3,000.00 of shared monthly expenses with a 50/50 split and a proportional split, for a household with a different income gap. Figures are illustrative.
When both incomes are equal
Partner A and Partner B each earn $4,000.00 a month.
| Figure | 50/50 | Proportional |
|---|---|---|
| Partner A payment | $1,500.00 | $1,500.00 |
| Partner B payment | $1,500.00 | $1,500.00 |
| Partner A income share used | 37.5% | 37.5% |
| Partner B income share used | 37.5% | 37.5% |
When one partner earns twice as much
Partner A earns $6,000.00 a month and Partner B earns $3,000.00.
| Figure | 50/50 | Proportional |
|---|---|---|
| Partner A payment | $1,500.00 | $2,000.00 |
| Partner B payment | $1,500.00 | $1,000.00 |
| Partner A income share used | 25.0% | 33.3% |
| Partner B income share used | 50.0% | 33.3% |
When one partner earns four times as much
Partner A earns $8,000.00 a month and Partner B earns $2,000.00.
| Figure | 50/50 | Proportional |
|---|---|---|
| Partner A payment | $1,500.00 | $2,400.00 |
| Partner B payment | $1,500.00 | $600.00 |
| Partner A income share used | 18.8% | 30.0% |
| Partner B income share used | 75.0% | 30.0% |
The payment columns above are exact. The income-share columns are rounded to one decimal place, so two figures that round to the same percentage are not always identical to the cent underneath.
Splitting money left over is a separate question from splitting the bill. In the third case, Partner A keeps $5,600.00 and Partner B keeps $1,400.00 after paying their proportional share — proportional splitting does not equalize what is left over, only the share of income each partner puts toward the shared expense.
To see these figures for your own household, you can try the calculator with your own numbers.
What the formula leaves out
Both methods only look at monthly income and the shared expense total. Neither one accounts for money either partner has already set aside, existing personal debts, unpaid care work, or assets one partner brings into the household. A partner with a smaller income might also carry more unpaid work or different debts — none of that is part of this comparison.
There is no salary-gap threshold built into either method that decides when to switch from one to the other. That is a decision for the two of you to make, based on more than the income figures above.
Choose a method you can revisit
Whichever method you choose, you can revisit it later. Incomes change, shared costs change, and an agreement that fit at the start of a relationship does not always fit years later.
If you want to weigh 50/50 and proportional splitting against two other approaches, you can see the four ways couples split expenses. If you want to see how Fairmony applies a proportional split to everyday expenses, read how Fairmony applies an income-based split.
Frequently asked questions
Is 50/50 unfair when incomes differ?
It creates equal payments but can create different income burdens. Whether that fits your relationship depends on the agreement and circumstances beyond income alone.
Does proportional splitting equalize money left over?
No. It uses the same income proportion for shared bills. The higher earner will usually still have more income remaining.
Is there a salary gap where we should switch?
This calculator does not prescribe a threshold. Compare the impact and agree on a method that accounts for your situation.
Can some expenses stay 50/50?
Yes. You can agree to split some shared expenses equally and use another method for others.
Try an income-based split in Fairmony
Fairmony tracks shared expenses for couples and can apply an income-based split, a 50/50 split, or a custom percentage to each one.
