Rent Calculator
Two Different Questions, One Calculator
"How much rent can I afford?" and "how do we split the rent fairly?" are the two most common rent math problems, and they have almost nothing in common mathematically — the first is a budgeting question against your income, the second is basic division across housemates. This tool handles both, switching the input set based on which one you're actually trying to solve.
The Formula
For affordability, the calculator checks two limits and recommends the lower one:
Max Rent (debt-to-income) = (Monthly Income × 36%) − Other Monthly Debts
Recommended Rent = the lower of the two
For splitting rent among roommates:
Why the Lower of Two Limits Matters
- The income rule (commonly 30% of gross income) is the number most people quote, but it ignores what else you owe.
- The debt-to-income limit caps total monthly obligations — rent plus car payments, student loans, credit cards — at 36% of gross income, a threshold many landlords and lenders actually screen against.
- Someone with no other debt will usually find the income rule is the binding constraint; someone carrying a car payment and student loans may find the DTI limit caps them well below 30% of income.
- Roommate splits get contentious fast when utilities are folded in unevenly — dividing the combined total keeps the math transparent and equal.
Income-Based Rent Limits at Different Percentages
Applied to a $6,000/month gross income, here's how the recommended ceiling shifts with the rule percentage used:
| Rule | Max rent (income-based) |
|---|---|
| 25% | $1,500.00 |
| 28% | $1,680.00 |
| 30% | $1,800.00 |
| 35% | $2,100.00 |
Actual affordability also depends on the 36% debt-to-income cap applied in the calculator — a high rule percentage doesn't help if other debts already eat into that limit.
How to Use This Calculator
- Choose "How Much Rent Can I Afford?" or "Split Rent Among Roommates" from the mode selector.
- For affordability: enter Gross Monthly Income, any Other Monthly Debt Payments, and optionally change the Rule % of Income (defaults to 30).
- For splitting: enter Total Monthly Rent, Monthly Utilities, and the Number of Roommates.
- Select Calculate to see the recommended rent ceiling or the per-person share.
Related Calculations
Once you have a rent ceiling, compare it against buying with the Rent vs Buy Calculator, or check what income a comparable home purchase would require using the Housing Affordability Calculator.