The Math Your Lender Hopes You Never Run
Meet Jordan. He has a 350,000 mortgage at 6.5% on a 30-year term, with a payment of about2,212 a month. He assumes he will pay it for 30 years because that is what the paperwork says. Then he runs the numbers on what happens if he adds just $200 a month. The result stops him cold: he pays the loan off in roughly 24 years instead of 30, and he saves around $109,000 in interest. That is the math nobody volunteers at closing.
Why extra payments hit so hard. Early in a mortgage, the overwhelming share of each payment goes to interest, not principal. In Jordan's first year, more than $22,000 of his roughly $26,500 in payments is pure interest. Every extra dollar you send goes straight to principal, which shrinks the balance that future interest is calculated on. You are not just paying down the loan, you are killing the interest that loan would have generated for years.
Three ways to attack it. You can add a fixed amount every month, make one larger payment each year, or drop a lump sum from a bonus or tax refund. This calculator lets you model all three. A 5,000 one-time payment in year three of Jordan's loan saves him far more than a5,000 payment in year twenty, because the early dollar has more time to compound in his favor.
The biweekly trick. Paying half your mortgage every two weeks results in 26 half-payments a year, which equals 13 full payments instead of 12. That one extra payment a year can shave four to six years off a typical 30-year loan without you ever feeling a big monthly hit.
The honest counterpoint. Paying off a mortgage early is not always the mathematically optimal move. If your rate is low and you could earn more investing the difference, the calculator on this page shows the guaranteed interest savings so you can weigh that certain return against an uncertain market one. Knowing the exact number is the first step to making the call that fits your goals.