Finance & Money
Mortgage Amortization Calculator
Use this mortgage amortization calculator to understand the payment and how much of the early payment goes to interest.
Monthly principal and interest
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- Total interest
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- First-month interest
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Study path
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What mortgage amortization means
Amortization is the schedule that splits every fixed mortgage payment between interest and principal. The payment stays the same each month, but the mix inside it shifts: early payments are mostly interest, and later payments are mostly principal. This calculator estimates the monthly principal-and-interest payment, the lifetime interest, and how the very first payment splits.
The amortization payment formula
P is the loan amount, r is the monthly rate (annual rate divided by 12), and n is the total number of monthly payments. Each month, interest equals the remaining balance times r; whatever is left of the payment reduces principal. Because the balance shrinks over time, the interest slice shrinks with it.
Why the first payment is interest-heavy
First month of a $350,000 loan at 6.75% for 30 years
Monthly rate is 6.75% / 12 = 0.5625%. First-month interest is $350,000 x 0.005625 = $1,968.75. If the payment is about $2,270, only around $301 goes to principal in month one. That ratio flips gradually over the life of the loan.
| Term | Typical trade-off |
|---|---|
| 30 years | Lower monthly payment, more total interest, slower principal paydown |
| 15 years | Higher monthly payment, less total interest, faster equity build |
- Total interest = monthly payment x number of payments - loan amount.
- Extra principal payments shorten the schedule and reduce total interest, since future interest is charged on a smaller balance.
- Rates vary by market, borrower, and loan type; any rate you enter here is illustrative, not a quote.
How to use it
- Enter loan amount.
- Enter rate and term.
- Compare monthly payment and lifetime interest.
How to read the answer
Early mortgage payments are interest-heavy; principal share grows over time.
Common mistakes and edge cases
- This is principal and interest only.
- Taxes, insurance, HOA, and PMI are not included.
- A shorter term usually raises payment but lowers total interest.
Worked examples
30-year mortgage
Monthly principal and interest
$2,270.09
15-year mortgage
Monthly principal and interest
$2,109.64
Frequently asked questions
Is this the full mortgage payment?+
No. It estimates principal and interest only.
Why is first-month interest so high?+
Interest is based on the remaining balance, which is largest at the start.
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Last updated: May 8, 2026