Mortgage Calculator
Monthly repayment, total interest and a year-by-year balance, with overpayment savings.
Calculate a Mortgage Payment and See Where the Money Goes
The repayment figure a lender quotes comes from one formula, and it is worth being able to check it yourself before you commit to twenty-five years of it. What moves that number most is not the price of the house but the rate and the term.
This calculator uses the standard amortised repayment formula and shows the year-by-year balance alongside it — the breakdown that makes plain how heavily early payments lean toward interest. It also takes an optional monthly overpayment, which is where the table becomes genuinely persuasive.
Key features
- The lender’s own formula — the standard amortised repayment calculation, so the monthly figure matches the one you will be quoted.
- Total interest over the term — the number that makes the case for a shorter term all by itself.
- Year-by-year balance — principal paid, interest paid and what is left owing at the end of each year.
- Overpayment modelling — add a monthly extra and see the interest and the years it removes.
- Principal and interest only — tax, insurance and service charges are not included, and the tool says so rather than quietly folding in a guess.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Mortgage Calculator
- Enter the property price and deposit
The loan amount is the difference, and it updates as you type. - Set the rate and term
Your annual interest rate and the length of the mortgage in years. These two move the payment far more than the price does. - Try an overpayment
Add a monthly extra, even a small one, and watch the total interest and the payoff date change. - Read the schedule
The monthly payment appears immediately; the year-by-year table shows how the balance actually falls.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Calculators |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Why is so much of my early payment interest?
Interest is charged on the outstanding balance, which is at its highest at the start. On a 30-year mortgage the first payment is typically 70–80% interest. The balance only falls meaningfully in the second half of the term, which is why early overpayments are so effective.
Does this handle a tracker or variable rate?
It assumes a fixed rate for the whole term. For a variable rate, model the current rate to see today’s payment, then rerun it with a higher rate to see what a rise would cost — that second number is the one worth knowing.
Does the payment include tax and insurance?
No. This is principal and interest, which is what the mortgage itself costs. Property tax, buildings insurance, PMI and service charges are collected separately and sit on top — budget for them, but do not expect them in this figure.
Are my figures sent anywhere?
No. Everything is calculated in your browser. No lender, broker or advertiser sees what you entered.