40x rule formula
Multiply monthly rent by 40 to estimate the annual gross income target. A $2,000 apartment maps to about $80,000 in annual gross income under this rule.
Why it matches the 30 percent arithmetic
Dividing annual income by 40 produces the same number as multiplying monthly income by 30 percent: annual income divided by 40 equals annual income divided by 12, multiplied by 0.30.
What it does not include
The rule does not include utilities, debt, savings, application standards, guarantors, credit checks, deposit rules, or local housing law. Treat it as a screening estimate only.
Household income and roommates
First confirm whose income the property will accept and how it treats co-applicants, guarantors, bonuses, tips, self-employment, or irregular income. Do not automatically add every roommate's income unless the listing's written screening policy allows that combination.
For a $2,400 apartment, 40x arithmetic produces $96,000 annual income. Two applicants earning $48,000 each reach that total mathematically, but the property still decides which documents and applicants qualify.
Compare the lease cost after the screen
Passing a gross-income screen does not show whether the lease fits take-home pay. Add required fees, utilities, insurance, parking, debt payments, savings, and living costs before deciding. The main planner identifies which comparison becomes the limiting one.