How the math works
Two rules govern this calculator. The 30 percent rule says housing should cost no more than 30 percent of gross monthly income: max rent = income x 0.30. The 3x income rule is what landlords actually enforce: most require gross income of at least 3 times the rent, so max rent = income / 3. The recommended max is whichever is lower.
Worked example
Monthly income of $4,000 with $300 in debts. The 30 percent rule gives $1,200. The 3x rule gives $1,333. The recommended max is $1,200, leaving $4,000 - $300 - $1,200 = $2,500 for everything else.
What the rules miss
Neither rule knows your other costs. High childcare, medical bills, or debt payments can make even 30 percent unaffordable, while a debt-free renter might stretch a bit higher safely. In expensive cities many renters exceed 30 percent; if you do, budget it explicitly rather than letting savings quietly drain. Read the full how much rent can I afford guide for the 50/30/20 method and landlord requirements.
Limitations
This calculator uses gross income and does not account for taxes, regional cost differences, utilities, or roommate splits. Some landlords require 3.5x or 4x income in competitive markets.