Mortgage calculator
Work out your monthly mortgage payment, total interest and total cost. Works for US and UK repayment mortgages.
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How this mortgage calculator works
This calculator uses the standard amortization formula used by banks in the United States and the United Kingdom. Enter your loan amount, annual interest rate and term in years, and it instantly shows your fixed monthly repayment, the total interest you'll pay over the life of the loan, and a principal-vs-interest breakdown.
Every fixed-rate repayment mortgage follows the same shape: early payments are mostly interest, and later payments are mostly principal. Over a 30-year loan, the crossover point — where more of your payment starts going to principal than interest — typically lands somewhere around year 15–18, depending on your rate.
Mortgage components explained
- Principal — the amount you actually borrowed (home price minus down payment).
- Interest rate — the annual cost of borrowing, expressed as a percentage (APR incorporates fees too — useful for comparing lenders).
- Term — how many years you have to repay. Shorter terms mean higher monthly payments but far less total interest.
- Down payment — cash paid upfront. In the US, putting down less than 20% usually triggers PMI (private mortgage insurance); in the UK, a bigger deposit unlocks better rate tiers.
Tips to lower your monthly payment
- A longer term lowers the monthly payment but increases total interest.
- Even a 0.5% lower rate can save thousands over a 30-year term.
- A larger deposit (down payment) reduces both payment and interest.
- Making one extra payment a year can shave several years off a 30-year term — see our compound interest calculator to model overpayments.
Frequently asked questions
How is a monthly mortgage payment calculated?
The payment uses the amortization formula M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r the monthly rate and n the number of payments.
Does this work for UK mortgages?
Yes — the repayment formula is identical. Just enter pounds instead of dollars.
Are taxes and insurance included?
No. Results show principal and interest only; taxes, insurance and fees vary by lender and location.
Why does most of my early payment go to interest?
Interest is charged on the remaining balance, which is highest at the start. As the balance shrinks, less of each payment goes to interest and more goes to principal — this is why the donut above shifts over the life of the loan.
This calculator provides estimates for information only — not financial advice. Results will vary by lender, credit profile and market conditions. Consult a qualified financial adviser before making financial decisions.