Amortization Calculator
See how a loan payment splits between interest and principal over time.
Your figures
Result
How to use this tool
- Enter your own figures over the defaults — Loan amount, Rate, Term.
- The answer updates as you type. There is no button, and nothing is sent anywhere.
- Change Rate on its own to see how much it moves the result — the worked example below shows exactly that.
Amortisation is front-loaded with interest. On a 30-year mortgage it typically takes about 18 years before you have repaid half the principal, even though you are halfway through the payments.
How it works
This takes 3 inputs — loan amount, rate, term — and returns monthly payment, interest in year 1, principal in year 1, balance after 1 year and halfway point reached at. The whole calculation happens in this page as you type: there is no submit button, no request, and nothing stored.
Because it recalculates on every keystroke you can use it as a sensitivity test rather than a one-shot answer. Moving rate alone from 6.5 to 7.5 changes monthly payment from 1,580.17 to 1,748.04 — the worked example below sets that out in full.
A worked example
Worked through with the figures the page already has in it: loan amount of 250,000 and rate of 6.5 %, and the rest as shown, giving monthly payment of 1,580.17. These numbers come from running the calculator’s own code, not from being typed in here, so they cannot drift away from what you see on screen.
Starting from:
- Loan amount: 250,000
- Rate: 6.5 %
- Term: 30 years
| Result | Value |
|---|---|
| Monthly payment | 1,580.17 |
| Interest in year 1 | 16,167.73 |
| Principal in year 1 | 2,794.31 |
| Balance after 1 year | 247,205.69 |
| Halfway point reached at | 21 yr 5 mo |
What happens when one input moves
Holding everything else steady and changing Rate from 6.5 % to 7.5 % — one percentage point — moves the answer like this:
| Figure | 6.5 % | 7.5 % |
|---|---|---|
| Monthly payment | 1,580.17 | 1,748.04 |
| Interest in year 1 | 16,167.73 | 18,671.85 |
| Principal in year 1 | 2,794.31 | 2,304.59 |
| Balance after 1 year | 247,205.69 | 247,695.41 |
| Halfway point reached at | 21 yr 5 mo | 22 yr 1 mo |
That is usually the number worth arguing over: it is easier to move than the headline amount, and the difference compounds across the whole term.
Amortization Calculator — frequently asked questions
Why is so little principal repaid early on?
Interest accrues on the outstanding balance, which is at its highest at the start. As the balance falls, the interest portion shrinks and the principal portion grows.
When do I reach the halfway point?
Later than you would expect. The calculator shows exactly when your balance falls below half the original loan — usually well past the midpoint of the term.
How do extra payments help?
An extra payment goes entirely to principal, removing that amount from every future interest calculation. Early extra payments are worth far more than late ones.
Is this calculator free?
Yes, with no account, no limits and no data collection. It runs entirely in your browser.
Should I rely on this for a financial or medical decision?
No. It is a planning estimate built on standard formulas and stated assumptions. For decisions that matter, speak to a qualified professional who can account for your full circumstances.
How accurate is the Amortization figure?
The arithmetic is exact. With the defaults on this page — loan amount 250000, rate 6.5 %, term 30 years — it returns monthly payment of 1,580.17. What limits accuracy is the assumptions, not the maths: change rate to 7.5 % and the same formula gives 1,748.04. Treat it as a well-founded estimate, not a quotation.
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Background reading: Loan, Mortgage and Investment Calculators Explained
Nothing is sent anywhere. The figures you type stay in this page and are never transmitted or stored — how that works.
Disclaimer. The formula is exact; the answer is only as good as the figures and assumptions above. Not financial, tax, medical or legal advice. Full disclaimer.