Mortgage Amortization Calculator · Practical guide
How Much of My Mortgage Payment Goes to Interest?
Early on, almost all of it — the interest share falls every single month as your balance shrinks.
At a glance
The Short Answer
Each month's interest equals your current balance times the monthly rate. On a new $300,000 loan at 6.5%, that is 300,000 × 0.005417 = $1,625.00 of interest in the first $1,896.20 payment — about 86%. Only $271.20 reduces the loan.
Interactive tool
Mortgage Amortization Calculator
Enter your own values, then compare the result with the examples below.
Results
Amortization Schedule
| # | Date | Payment | Principal | Interest | Balance |
|---|
How the Split Changes Over Time
| Payment | To Interest | To Principal | Interest Share |
|---|---|---|---|
| #1 | $1,625.00 | $271.20 | 86% |
| #12 | $1,608.40 | $287.81 | 85% |
| #233 | $946.50 | $949.70 | 50% |
| #360 (final) | $10.22 | $1,885.99 | 0.5% |
Why It Works This Way
The payment is fixed, but interest is recalculated monthly on the remaining balance. Every dollar of principal you pay shrinks next month's interest charge slightly, freeing a slightly larger slice of the payment for principal — a snowball that starts painfully slow and ends fast.
What Speeds Up the Shift
- A lower rate — at 5% the first payment is only 72% interest instead of 86%.
- A shorter term — on a 15-year loan at 6.5%, the first payment is already 38% principal.
- Extra payments — every extra dollar is 100% principal, permanently lowering the interest share of every future payment.
Frequently Asked Questions
How do I find the interest portion of my next payment?
Multiply your current balance by your annual rate divided by 12. A $250,000 balance at 6% accrues 250,000 × 0.005 = $1,250 of interest that month.
Does my escrow payment affect this split?
No. Taxes and insurance collected in escrow sit outside the loan entirely. The interest-principal split applies only to the principal-and-interest portion of your payment.
When does more than half my payment go to principal?
On a 30-year loan at 6.5%, around payment 233 — about 19 years and 5 months in. Lower rates and shorter terms reach the crossover much sooner.
Why did my interest portion barely move after several years?
Early balances fall so slowly that the split improves by only a few dollars a month at first. The improvement accelerates noticeably after the halfway point of the term.