Early in a mortgage most of each payment is interest; by the end it’s almost all principal. On a 30-year loan at 6.5%, it takes about 20 years before more than half of each payment goes to principal.
How to use the Mortgage Amortization Calculator
- Loan amount
- Interest rate
- Loan term
- After how many years?
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the loan details and the number of years to look at.
Inputs explained
| Field | What to enter |
|---|---|
| Loan amount | Amount in your currency |
| Interest rate | In % |
| Loan term | Units: years, months |
| After how many years? | A number |
What each result means
- Monthly payment = pmt([Interest rate]÷1200, [Loan term], [Loan amount])
- Remaining balance = max(bal([Loan amount], [Interest rate]÷1200, [Loan term], min([After how many years?]×12, [Loan term])), 0)
- Principal paid so far = [Loan amount] – [Remaining balance]
- Interest paid so far = [Monthly payment]×min([After how many years?]×12, [Loan term]) – [Principal paid so far]
- First payment (interest part) = [Loan amount]×[Interest rate]÷1200
- First payment (principal part) = [Monthly payment] – [First payment (interest part)]
- Total interest over the loan = [Monthly payment]×[Loan term] – [Loan amount]
- Equity from paydown = [Principal paid so far]÷[Loan amount]×100
Example values
How the main result changes when Loan amount changes and everything else stays at the example values above:
| Loan amount | Monthly payment |
|---|---|
| 160,000 | 1,011.31 |
| 240,000 | 1,516.96 |
| 320,000 | 2,022.62 |
| 400,000 | 2,528.27 |
| 480,000 | 3,033.93 |
| 640,000 | 4,045.24 |
Formula
Payment M = P × i ÷ (1 − (1 + i)^−n)
Balance after k payments = P(1 + i)^k − M[(1 + i)^k − 1] ÷ i
Principal paid = P − balance; interest paid = k × M − principal paid
Worked example
Inputs: Loan amount: $320,000; Interest rate: 6.5 %; Loan term: 30 years; After how many years?: 5.
Results: Monthly payment = $2,022.62; Remaining balance = $299,555.13; Principal paid so far = $20,444.87; Interest paid so far = $100,912.19; First payment – interest part = $1,733.33; First payment – principal part = $289.28; Total interest over the loan = $408,142.36; Equity from paydown = 6.39 %.
Frequently asked questions
What is amortization?
Paying off a loan with regular payments that cover interest and principal.
Why is most of my payment interest at first?
Interest is charged on the balance, which is largest at the start.
When do I pay more principal than interest?
On a 30-year loan at 6–7%, after roughly 18–21 years.
Sources
Guides on this topic
- How to Calculate a Mortgage Payment (Formula + Example): The mortgage payment formula explained step by step, with a worked example, what PITI adds on top, and how rate, term, down payment and extra payments change what you pay.