How extra mortgage payments work
Every dollar of extra payment goes straight to principal — the amount you still owe. That matters because interest each month is charged only on the remaining balance. Knock the balance down faster and there is simply less left for future interest to grow on, so your savings compound month after month.
The effect is larger than most people expect. Because a 30-year loan front-loads interest, a small extra amount early on removes principal that would otherwise sit on the books — accruing interest — for decades. Adding even a few hundred dollars a month can shorten the loan by years and save tens of thousands of dollars in total interest.
This tool builds two amortization schedules at the same rate — one with your normal payment and one with the extra applied each month — and compares the total interest and payoff time. The full method and assumptions are on our methodology page. This calculator is for education, not advice.
Frequently asked questions
- How much can extra mortgage payments save me?
- It depends on your balance, rate and how much extra you add, but the savings are often large. Because every extra dollar goes straight to principal, you stop paying interest on that dollar for the entire remaining life of the loan. On a typical 30-year mortgage, even a few hundred dollars a month can cut years off the term and save tens of thousands in interest.
- Is it better to pay off my mortgage early or invest?
- Paying extra on the mortgage gives you a guaranteed, risk-free return equal to your interest rate. Investing may earn more over the long run but is not guaranteed and is taxed differently. Many people split the difference, or prioritise whichever rate is higher after accounting for tax and risk tolerance.
- Does this store my numbers?
- No. Everything runs in your browser. Nothing you type is uploaded or saved on a server.