How it works

A fixed-rate loan is repaid in equal monthly instalments. Each payment covers the interest due that month plus a slice of the principal, so early payments are mostly interest and later ones mostly principal.

The payment comes from the amortization formula M = P × i / (1 − (1 + i)−n), where P is the loan amount, i is the monthly rate (annual rate ÷ 12) and n is the number of monthly payments. Total interest is simply every payment added up, minus the amount you borrowed.

Worked example

Borrow $300,000 at 6.5% over 30 years and the payment is about $1,896 a month. Across 360 payments you repay roughly $682,600 — meaning around $382,600 of it is interest.

Frequently asked questions

Does this include property tax or insurance?
No — it shows principal and interest only. Add your local tax, insurance and any HOA fees separately to get a full housing cost.

Can I use it for car loans or personal loans?
Yes. Any fixed-rate, fixed-term loan works — just enter the amount, rate and term.

How do I lower the total interest?
A shorter term or a lower rate both cut total interest sharply. Try changing the term to see the effect instantly.