Your result
What your result means
Each month of this $300,000 loan costs $1,896.20. In month 1 only $271.20 of that reduces the balance and $1,625.00 is interest, because interest is charged on the full balance. As the balance falls, the split tilts toward principal: after five years you will have repaid $19,167, and the balance drops below half the original amount in year 22. Over the whole term interest adds up to $382,637.
The math
Formula and sources
M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)
Each month: interest = balance × r (rounded to the cent)
principal = M − interest
new balance = balance − principal- M
- monthly principal-and-interest payment
- P
- amount borrowed (price minus down payment)
- r
- monthly interest rate = annual rate ÷ 12
- n
- number of monthly payments = years × 12
We round each month’s interest to the cent and let the final payment absorb any leftover cents, which is how loan servicers build real schedules.
Sources we checked this against
- 1Loan Estimate sample H-24(B), fixed-rate loanConsumer Financial Protection Bureau · files.consumerfinance.gov
- 2PPMT function (principal part of a payment)Microsoft Support · support.microsoft.com
- 3PMT function (payment formula and examples)Microsoft Support · support.microsoft.com
Formula last checked 2026-11-04. Found an error? Tell us and we will fix it.
Step by step
Two worked examples
CFPB sample loan
Monthly payment
$761.78
- Loan amount
- $162,000
- Interest rate
- 3.875%
- Loan term
- 30 years
This is the loan on the CFPB’s sample Loan Estimate. The payment is $761.78; month 1 splits into $523.13 interest and $238.65 principal. After five years $15,773 of principal is repaid, matching the $15,773 on page 3 of the form.
Same balance, 15 years
Monthly payment
$1,188.17
- Loan amount
- $162,000
- Interest rate
- 3.875%
- Loan term
- 15 years
Halving the term raises the payment to $1,188.17, but month 1 already sends $665.04 to principal, five-year principal repaid jumps to $43,952, and total interest falls to $51,871.
| Result | Example 1 | Example 2 |
|---|---|---|
| Monthly payment | $761.78 | $1,188.17 |
| Principal repaid in first 5 years | $15,773 | $43,952 |
| Balance falls below half in year | 20 | 9 |
| Total interest | $112,244 | $51,871 |
Questions
Frequently asked questions
Why does so much of my early payment go to interest?
Interest each month is the balance times the monthly rate. Early on the balance is at its largest, so the interest portion is too. The payment stays fixed, so every dollar of principal you repay lowers next month’s interest and shifts the split.
Does the schedule include taxes and insurance?
No. An amortization schedule covers only principal and interest. Escrow items do not reduce the loan balance.
How do extra payments change the schedule?
Extra principal lowers the balance immediately, so every later month has less interest and the loan ends early. Try the extra payment calculator to see the new payoff date.