What this calculator does
A fixed-rate loan spreads principal and interest across equal monthly payments. Early payments are interest-heavy; later payments reduce principal faster.
This calculator shows the monthly payment, total interest and payoff time, and lets you add an extra monthly payment to see the savings. The first 12 payments are broken down.
Loan payment
Payment = P × r ÷ (1 − (1 + r)^−n) P is the principal, r the monthly interest rate and n the number of months. Extra payments go directly to principal and shorten the term.
How this calculator works
- 01
Enter the loan amount
Use the amount borrowed before fees and insurance.
- 02
Add rate and term
Enter the annual rate and the term in years.
- 03
Test extra payments
Add an optional monthly extra to see the interest saved and the earlier payoff.
Frequently asked questions
Does this include taxes and insurance?
No. Property taxes, insurance, HOA fees and closing costs are separate. The calculator covers principal and interest only.
Is the rate fixed?
Yes, the model assumes a constant annual rate. Variable-rate loans can change and require a different projection.
How much does an extra payment help?
Even a small extra payment can cut years off a long loan because it reduces principal and future interest. The exact effect is shown in the results.
Data basis: 2026 · Annual constants live in structured JSON files and are updated once a year.
Results are unverified model calculations and do not replace tax, legal or financial advice.