Mortgage Payoff Formula Explained
The math behind the Mortgage Payoff Calculator: the equation, the variables, and the assumptions it makes.
By Onias Derilus, Mortgage Capital · NMLS# 1859012 · Last Updated: June 2026
It shows how quickly you can pay off your remaining mortgage balance under different extra-payment and lump-sum scenarios, and the interest you save.
The Formula
Payoff date depends on balance, rate, payment, and extra principal
Unlike the amortization calculator, which starts at the original loan, this one starts from your current balance, so it reflects where you are today rather than where you began.
A lump sum applied to principal removes its future interest entirely, while recurring extra payments accelerate the payoff steadily. The calculator quantifies the months and dollars saved for each approach.
Turn Your Mortgage Payoff Estimate Into a Real Pre-Approval
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Rates are illustrative only. APR and payments vary by credit score, loan amount, and market conditions. Subject to credit approval. Not a commitment to lend. NMLS# 1859012. Equal Housing Lender.