Mortgage Calculator

How to use Mortgage Calculator

1. Open Mortgage Calculator in your browser — it loads instantly and works offline once cached.
2. Enter your values in the input fields. Every field is labelled so you know exactly what to type.
3. The result updates automatically as you type — there is no "submit" round-trip to a server.
4. Adjust any input to compare scenarios and see how the outcome changes in real time.
5. Copy or note the result. Nothing you enter is stored or sent anywhere.

Why use Mortgage Calculator?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full financial calculators suite, so related mortgage tasks are one click away.

What people use Mortgage Calculator for

• Estimating a monthly repayment before speaking to a lender or broker.
• Comparing a 25-year term against a 30-year one on the same loan.
• Seeing the total interest cost over the life of a mortgage.

Mortgage Calculator: limits and things worth knowing

• The same amortisation formula as any loan, but the term makes the interest total dramatic: £250,000 at 4.5% over 25 years costs about £1,389 a month and £166,800 in interest.
• Extending 25 years to 30 lowers the payment by roughly £122 and adds about £39,000 in total interest — the standard trade-off worth seeing in numbers.
• This covers principal and interest only. Property tax, buildings insurance, service charges, ground rent and any mortgage insurance are all additional and can add a substantial amount.
• Most mortgages are fixed for an initial period and then revert to a variable rate, so a payment calculated at today's fixed rate is not the payment for the whole term.

Is it private and secure?

Your privacy is built in. Mortgage Calculator runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Why Browser-Based Tools Are Safer for Your Files — Most online converters upload your files to a server. Client-side tools don't. Here's why that difference matters for privacy.