How much the monthly repayment looks like
This is still the starting point, but it is not the only number that matters. The same payment can hide a very different total cost depending on the term and rate.
Mortgage Repayment Calculator
Mortgage calculator for monthly repayments, interest and balance schedules
Estimate the monthly mortgage payment first, then check the total interest, yearly balance path and interest-only comparison before treating the result as affordable.
Mortgage payment estimateTotal interest and scheduleRepayment versus interest-only view
Term Effect
Longer terms lower the payment but increase total interest
Balance View
The schedule shows how quickly the loan actually falls
Interest-Only
The lower payment still leaves the full capital to clear later
Planner
Start with the payment, then judge the long-term cost
Use the planner to test loan size, rate and term together. The result shows the monthly commitment, full-term interest and balance path behind the headline number.
Mortgage Details
£
%
years
Monthly Repayment
Monthly Payment
£1,389.58Total Repayable
£416,874Total Interest
£166,874Interest as % of Loan
66.75%Payment Breakdown
Principal repaid
£250,000
59.97% of total repaid
Interest paid
£166,874
40.03% of total repaid
This breakdown shows the total capital repaid versus total interest over the full term on the same rate and repayment structure.
What It Shows
The numbers worth checking before you treat a payment as affordable
A monthly figure on its own can hide the real trade-off. These are the parts of the calculation that usually change the decision.
How much interest the mortgage costs overall
Showing total interest changes the conversation from "can I make the monthly payment?" to "what is the long-run cost of choosing this term and rate combination?"
How quickly the balance actually falls
The repayment schedule matters because early payments are interest-heavy and later payments are much more capital-heavy. That time profile is what makes early overpayments so powerful.
What the calculation does not include
This route works on the mortgage amount only. Deposit, stamp duty, legal fees, surveys and moving costs still sit outside the repayment number and need their own planning tools.
Worked Examples
Use the examples to pressure-test rate and term changes
These examples use the same calculation logic as the planner, so they are useful for quick rate and term sense-checks.
| Interest rate | Monthly repayment |
|---|---|
| 4.0% | £1,319.59 |
| 5.0% | £1,461.48 |
| 6.0% | £1,610.75 |
| Term | Monthly repayment | Total interest |
|---|---|---|
| 25 years | £1,753.77 | £226,131 |
| 30 years | £1,610.46 | £279,767 |
| 35 years | £1,514.06 | £335,906 |
What these examples are meant to show
A repayment figure can look stable until you test a higher rate or a longer term. The tables are there to show how quickly total cost can move when only one input changes.
Interest-Only Context
Why the lower monthly payment can be the more dangerous number
The comparison tab is there to show structure, not to push the lower monthly figure as the better answer.
Interest-only lowers the payment by deferring the capital problem
An interest-only mortgage can make the monthly payment look easier, but the original loan is still there at the end of the term.
The repayment plan matters as much as the mortgage itself
The lower payment only makes sense if there is a credible plan for clearing the capital later. Without that, the cheaper-looking monthly figure is misleading.
Residential and buy-to-let uses are not the same
The interest-only route can show up in different ways across residential and investment cases, so a lower payment should never be read as a universal sign that the structure is better.
Repayment maths is often the safer planning baseline
Even when you later compare product structures, repayment provides the cleanest baseline because it shows the cost of actually clearing the debt rather than postponing the principal.
Next Tools
Use the adjacent tools once the repayment baseline is clear
The next step depends on what question is still open after the payment and schedule make sense.
Overpayment Calculator
Move here if the real question is how quickly you can cut interest once the base repayment is affordable.
Stress Test Calculator
Use the stress test if you want to see how far the payment moves when the rate rises.
Fees and Costs Calculator
Add the wider buying budget so the mortgage payment is not mistaken for the full cost of purchase.
Affordability Calculator
Check the borrowing range before treating the repayment result as a workable purchase budget.
Frequently Asked Questions
How is a monthly mortgage repayment calculated?
This calculator uses standard repayment mortgage maths based on the mortgage amount, interest rate and term. The result is an indicative payment estimate, not a mortgage offer or affordability decision.
What is the difference between repayment and interest-only?
A repayment mortgage reduces the capital and the interest over time. An interest-only mortgage only covers interest during the term, so the original loan still has to be repaid separately at the end.
Does a longer mortgage term always help?
A longer term usually lowers the monthly payment, but it can materially increase total interest. The planner shows both the payment and the total-interest effect instead of only the headline monthly figure.
Does this calculator include stamp duty, deposit or legal fees?
No. The planner works on the mortgage loan only. You still need a separate budget for deposit, stamp duty, legal fees, surveys, removals and other buying costs.
Can I rely on the interest-only comparison as product advice?
No. Interest-only only looks cheaper month to month because the capital is not being repaid during the term. You still need a credible way to clear the full balance at the end, and product availability depends on the lender and the case.