Loan Payoff Time Calculator

Calculate how long it will take to pay off a loan with fixed monthly payments. See total interest and payoff schedule.

This calculator solves for Payoff Time by inverting the fixed-payment amortization formula (line 57): months equals negative the natural log of one minus principal times the monthly rate divided by Monthly Payment, all divided by the natural log of one plus the monthly rate. If Annual Interest Rate is entered as exactly 0%, that logarithmic formula is skipped entirely in favor of a simple division, Payoff Time equals Loan Amount divided by Monthly Payment (lines 9-10) — an exact-equality branch, not an approximation for a very low rate. Payoff Months is moved by Loan Amount and Monthly Payment in exactly equal and opposite amounts across a ±10% probe, about 23% each, while Annual Interest Rate barely moves it, under 2%, at the default 5% rate — the payment size and the debt size matter far more to how long payoff takes than the interest rate does, at least at a modest rate. Total Interest, by contrast, is dominated by Loan Amount (about 43%), well ahead of Monthly Payment (about 21%) and Interest Rate (about 14%). Because the payoff-time formula involves a logarithm of a quantity that must stay positive, a Monthly Payment at or below the interest accruing every month — about $41.67 at the default $10,000 principal and 5% rate — makes that logarithm's argument non-positive, and the calculator returns no usable result at all rather than a warning or a very large number. Even a payment of $42, just thirty-three cents above that floor, still takes 1,164 months, about 97 years, to pay off, showing how steep the payoff curve gets near the break-even point. This calculator assumes the payment and rate stay fixed for the whole payoff, with no missed payments or rate changes along the way.