Mortgage guides

Mortgage Payment Calculator (UK)

Use this mortgage calculator to test whether a property price still feels workable once deposit, rate, term, fees and future rate pressure are considered together. It is built to answer a planning question, not a borrowing-power question: “if I buy at this level, what does the payment path look like and how exposed am I if the deal changes later?”

Written byMyFinanceTools Editorial
Reviewed1 April 2026
Use it forRepayment mortgage planning

Key takeaways

  • This page is most useful when you are pressure-testing a property budget before an offer or remortgage decision.
  • Affordability is not the same as borrowing power. A lender may allow more than still feels comfortable in your monthly budget.
  • Deposit size, product fee, introductory rate and the likely follow-on rate can matter more than the headline starting payment.

Decision one

Can the payment stay sensible beyond the headline deal?

A mortgage can look manageable at the opening rate and still become weak once the fixed period ends. The first job is to test resilience, not optimism.

Decision two

Is the deposit improving the deal enough?

A slightly stronger deposit can reduce the loan, improve loan-to-value and open better pricing. That can matter more than stretching the term.

Decision three

Are you reducing the payment or just delaying the cost?

A longer term lowers the monthly figure, but the trade-off can be years of extra interest. This page is designed to make that trade-off visible.

Before you calculate

Use this page to judge the deal, not to prove you can borrow

A mortgage calculator is most useful before a viewing shortlist turns into an offer. It helps you test whether the payment still makes sense once deposit size, fees, term length and a more realistic later rate are taken seriously. That is a stronger question than “what is the monthly payment on a good day?”

This page cannot tell you what a lender will formally approve, how underwriting will view your income, or whether a specific product will still be available. It also cannot capture every product feature, early repayment charge or lender rule. What it can do well is help you compare realistic scenarios so you can discard weak ones early.

Calculator

Model the payment path before you commit

Keep the inputs practical. Start with a realistic property price, then test the deposit, introductory rate, likely follow-on rate and any overpayments you could actually sustain. The strongest use of this tool is comparison rather than prediction.

Calculator

Enter your details and select Calculate to view estimated monthly repayments and overall costs.

Used for formatting results.
Total purchase price of the property.
Length of the mortgage.
Choose amount or %.
Choose deposit type above.
Rate during the initial deal period.
Years before the follow-on rate starts.
Rate assumed after the initial period ends.

Results

Your estimated mortgage summary appears here after calculation.

Mortgage snapshot
—

Calculate to see the repayment picture for this scenario.

Loan-to-value—
Deposit used—
All-in cost —
Total mortgage paid—
Deposit—
Monthly payment (intro)—
Monthly payment (after intro)—
Total interest—
Total paid—
Payoff time—
Interest saved—
Upfront fees—
Loan amount used—
Estimated borrowing based on a loan amount of —. Use the schedule to see how interest and balance change month by month.

Interpret the result

What this calculator can tell you well

It can show whether a property still looks sensible once you move beyond the best-case monthly payment. It can show how much extra interest a longer term creates, what happens when a better deposit reduces the loan, and how a fee-heavy product can change the overall picture. It is especially useful for comparing two or three scenarios side by side before you talk to a lender or broker.

It is less useful when you treat the first number as a borrowing target. Affordability is household-specific. Income volatility, childcare costs, service charges, insurance, repairs and future plans all matter. A result can look affordable and still be the wrong decision if it leaves too little room for normal life.

When the result can mislead

  • When the fixed period is short and the follow-on rate is ignored
  • When the payment only works because the term is unusually long
  • When a lower rate is chosen without accounting for product fees
  • When the budget is tested against lender maximums instead of home finances

Compare next

Run the next scenario before you trust the first one

The most useful follow-up comparisons depend on what is creating pressure. If the monthly payment is the issue, test a lower property price before extending the term. If the deal looks cheap but fees are high, compare a slightly higher rate with lower fees. If the payment works now but not after the intro period, model a stronger deposit or a safer budget target.

Bigger deposit vs longer term

A stronger deposit can improve both monthly cost and deal quality, often more cleanly than stretching the term.

Fees upfront vs added to loan

Paying fees upfront preserves a smaller balance. Adding them spreads the cost but increases interest over time.

Overpay later vs borrow less now

Overpayments help, but borrowing less from day one usually reduces risk more reliably.

What this page cannot tell you

It does not replace a full lender affordability check, a mortgage illustration, legal advice or a product comparison across the whole market. Use it to narrow the field, pressure-test assumptions and spot weak scenarios earlier.

Best way to use the result

Keep one optimistic scenario and one tougher one. If the tougher version still fits your budget comfortably, you have a much stronger basis for moving forward.

FAQ

Mortgage calculator questions

How are mortgage repayments calculated?

Repayments are based on the loan amount, rate and term. This calculator uses a standard repayment mortgage method where each payment covers interest and reduces the balance.

Why is affordability different from borrowing power?

Borrowing power is a lender decision. Affordability is your own budget decision. A lender may allow a higher loan than still feels comfortable after housing costs and normal spending.

Does a longer term always make the mortgage better?

No. It lowers the monthly payment but usually increases total interest. It can solve a short-term budget issue while making the long-run cost worse.

Should I compare fees as well as rates?

Yes. Two deals with similar rates can lead to different overall costs once arrangement fees and how they are paid are included.

Can this calculator replace a lender quote?

No. It is an estimate for planning and comparison. Product availability, underwriting, daily interest methods and fees can change the real figures.

Why model the follow-on rate?

Because the opening payment can understate the longer-run reality. A mortgage that only works during the introductory deal can become uncomfortable later.

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