Amortization Calculator
Work out the monthly payment on an amortizing loan plus the total interest and the number of payments you will make.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
Breakdown
About this calculator
For a fixed-rate loan with equal monthly payments, each payment covers that month's interest and reduces principal. This estimate assumes payments are made on schedule and excludes fees, insurance, taxes, refinancing and extra payments. It gives the monthly payment, total paid and total interest over the term.
Worked example
calculated with the default values below
Loan amount 200,000 $ · Annual interest rate 5 % · Loan term 30 years Monthly payment 1,073.64 $ · Total paid 386,511.57 $ · Total interest 186,511.57 $ · Number of payments 360
Data sources
Disclaimer
These calculators give estimates for general information only. They are not financial, tax or investment advice and do not take your personal circumstances into account. Before borrowing, investing or filing, confirm the numbers with a qualified adviser in your jurisdiction.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)
- M
- monthly payment
- P
- loan principal
- r
- monthly interest rate
- n
- number of payments
r = annual % ÷ 100 ÷ 12; n = years × 12.
Frequently asked questions
Why does almost none of my early payment reduce the balance?
Because interest is charged on whatever you still owe. At the start of a long loan the balance is at its largest, so most of each payment is interest and only a small slice touches the principal. That reverses slowly over the term, which is why extra payments made in the first few years save far more interest than the same money paid near the end.
Why can a longer loan term lower the monthly payment but raise total interest?
The calculator spreads the principal over the number of monthly payments you choose and applies the entered annual rate monthly. A longer term normally lowers each required payment but leaves a balance outstanding for more months. Compare the monthly payment and total-interest outputs together; this tool does not model refinancing, recasting or extra payments.