RENT AFFORDABILITY CALCULATOR
The 30% rule comes from a 1969 US housing law, not financial science. In high-cost cities (NYC, San Francisco, London), median renters often spend 40–50%+. Estimate to inform your search. Landlord approval and what you can comfortably afford will differ.
Updated May 2026 · Built by Lukáš, an architect in Prague.
Formula, assumptions, rounding & limitations
Formula
max rent = income × (rule ÷ 100) − (debts × 0.5)conservative = income × 0.20stretch = income × ((rule + 5) ÷ 100)
Assumptions
- Income and debts are monthly figures in the same currency.
- The rule defaults to 30%; you can change the percentage in the input.
- Debts are weighted at half. This is a simplified cash-flow adjustment used by this calculator, not a landlord rule.
- Both decimal comma (1 500,50) and decimal point (1500.50) are accepted.
Rounding
- Suggested max rent, conservative, and stretch values are rounded to the nearest dollar for display.
- If the formula yields a negative number (debts exceed income at the chosen rule), the result floors at zero.
Limitations
- Utilities, internet, renters insurance, parking, transit, groceries, and other monthly expenses are not subtracted.
- Landlord criteria (commonly income ≥ 2.5–4× rent), credit score, employment history, and rental history are not evaluated.
- Local rent control, security deposit caps, broker fees, pet rent, and utilities-included leases are not modelled.
- Estimate to inform your search. Landlord approval and what you can comfortably afford will differ.
Should I use gross or net income?
The 30% rule traditionally uses gross (pre-tax). This calculator works with whichever you enter — but using net income gives a more realistic ceiling because that’s what actually hits your account.
Why does this subtract half of my debts and not all?
Because debt payments aren’t going up if you sign a lease — they’re already in your budget. The half-adjustment is a heuristic to leave room for the part of debt servicing that competes with rent for the same monthly cash. Landlords often use a stricter “30% of (income − all debts)” calculation.
What do most landlords actually require?
The common landlord rule is gross monthly income ≥ 3× rent (so rent ≤ 33% of income). Some require 2.5× or 4×. Your credit score and rental history matter more than which exact ratio you fit.
Why does the 30% rule break in big cities?
Because rent is set by local supply and demand, not by national averages. In NYC, San Francisco, or central London, the median renter spends 40–50%. The rule is an old guideline, not a law of physics — the calculator gives you the math, you decide what fits your life.