Calculate your monthly payment, total interest cost, payoff date, and see a full amortization schedule. Supports extra payments, variable terms, and all loan types.
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Most loans use amortization, which means each monthly payment is a mix of interest and principal. The payment stays the same each month, but the proportion shifts over time: early payments are mostly interest, while later payments are mostly principal.
The standard loan payment formula is:
M = P × [r(1+r)n] / [(1+r)n − 1]
Where: M = monthly payment, P = principal (loan amount), r = monthly interest rate (annual rate / 12), n = total number of monthly payments.
For a $250,000 mortgage at 6.5% APR for 30 years:
r = 6.5% / 12 = 0.5417% per month, n = 360 months.
Monthly payment: $1,580.17. Over 30 years, you'll pay $568,861 total, meaning $318,861 in interest—more than the original loan amount.
Amortization is the process of gradually paying off a debt through regular payments over a set period. Each payment covers two components:
As the balance decreases, less goes to interest and more to principal. By year 20 of a 30-year mortgage, the split reverses—most of each payment now reduces the balance. This is why early extra payments are so powerful: they reduce the principal that future interest is calculated on.
Our calculator works for any fixed-rate amortizing loan. Here are the most common types:
Making extra payments toward your loan principal is one of the most effective financial strategies available. Even small additional payments can dramatically reduce total interest and shorten your loan term.
| Extra Payment | Payoff Time | Time Saved | Interest Saved |
|---|---|---|---|
| $0/month | 30 years | — | — |
| $100/month | 25 years, 2 mo | 4 years, 10 mo | $59,972 |
| $250/month | 21 years, 5 mo | 8 years, 7 mo | $119,326 |
| $500/month | 17 years, 9 mo | 12 years, 3 mo | $181,417 |
| $1,000/month | 13 years, 1 mo | 16 years, 11 mo | $238,478 |
Key insight: An extra $100/month on a $250,000 mortgage saves nearly $60,000 in interest and cuts almost 5 years off the loan. That's a massive return on a relatively small additional commitment. Even one extra payment per year (equivalent to $132/month extra) can shave 4+ years off a 30-year mortgage.
Small differences in interest rates have an enormous impact over the life of a loan, especially for large amounts and long terms. Here's how different rates affect a $300,000, 30-year mortgage:
| Rate | Monthly Payment | Total Interest | Total Paid |
|---|---|---|---|
| 5.0% | $1,610 | $279,767 | $579,767 |
| 5.5% | $1,703 | $313,212 | $613,212 |
| 6.0% | $1,799 | $347,515 | $647,515 |
| 6.5% | $1,896 | $382,633 | $682,633 |
| 7.0% | $1,996 | $418,527 | $718,527 |
| 7.5% | $2,098 | $455,157 | $755,157 |
Rate shopping matters: On a $300,000 mortgage, the difference between 6.0% and 6.5% is $97/month and over $35,000 in total interest. Getting quotes from at least 3–5 lenders and negotiating rate can save you tens of thousands of dollars over the life of your loan.