Home Mortgage Calculator

28% / 36% guideline: many lenders use a "front-end" ratio (housing payment ÷ gross monthly income) target of 28% or less, and a "back-end" ratio (housing payment + other debt payments ÷ gross monthly income) target of 36% or less, when evaluating loan qualification. These are general guidelines, not guarantees of approval — actual underwriting standards vary by lender and loan program. These ratios aren't calculated for an all-cash scenario, since there's no loan to qualify for.

This calculator does not include private mortgage insurance (PMI) or homeowner association special assessments. "Total interest over life of loan" reflects the original amortization schedule; the effect of an extra monthly principal payment is shown separately below.

Strategy 1 — fixed extra amount each month: the amount you enter is added to every monthly payment, starting with payment #1, applied entirely to principal, for as long as a balance remains.

Strategy 2 — one extra payment at year-end: your regular 12 monthly payments go as scheduled, and the amount you enter is paid as a single lump sum once a year (at the end of every 12th payment), applied entirely to principal.

Strategy 3 — match each month's principal reduction: no amount to enter. Every payment is increased by that same month's own scheduled principal portion — in effect doubling the principal paid down each month. Because the principal portion of a payment grows every month as the balance shrinks, this isn't a flat dollar amount; it recalculates every month.

Strategy 4 — biweekly payments: no amount to enter. Pays half of the regular monthly P&I payment every two weeks — 26 payments a year rather than 12 monthly payments — computed on its own biweekly interest schedule (not simply the monthly schedule split in half), which both adds the equivalent of one extra monthly payment per year and shortens the interval between payments.

All four assume your lender allows unrestricted extra principal payments with no prepayment penalty. Some loans charge a fee or place limits on extra principal payments, and formal biweekly programs run through a servicer sometimes carry their own setup fees — check your note/loan agreement before counting on this.