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5 min readNumbers only. No advice.

GBP400,000 Mortgage at 4.5% for 30 Years: Payment Example

Worked example for a GBP400,000 repayment mortgage at 4.5% over 30 years, designed for users comparing larger loans and longer terms.

Read the formula, then test the same idea with your own inputs.
Use the Mortgage Repayment Calculator

This extension page exists to support specific long-tail queries with formula-first explanations. It is intentionally narrow, deliberately opinion-free, and designed to lead into the relevant calculator rather than replace it.

Plain Figures does not recommend products, wrappers, or financial actions here. The goal is to make the arithmetic and the assumptions visible.

Core Formula

Amortisation with a longer term
M = P x [r(1 + r)^n] / [(1 + r)^n - 1]
  • P = GBP400,000 principal
  • r = 4.5% / 12 monthly rate
  • n = 30 x 12 monthly payments

Why the 30-year term changes the story

A 30-year term often makes a larger loan feel manageable because it spreads repayment over more months.

The trade-off is that the interest window becomes much longer, which can push lifetime cost materially higher.

How to use the page

This example works best as a baseline before testing 25-year or overpayment cases in the calculator.

It is useful precisely because it shows the gap between monthly affordability and total cost.

FAQ

Why is the monthly payment lower than a shorter-term mortgage?

Because principal is spread across more months, even though total interest rises.

Can overpayments offset the longer term?

Yes. Overpayments can shorten the term and reduce interest if the product allows them.

Disclaimer

Illustration only. This page shows the repayment maths for one input set and is not a product recommendation or lending assessment.
Use This Calculator

Open the matching calculator to apply the guide to your own numbers.

Use the Mortgage Repayment CalculatorRun your own numbers with the linked calculator after reading the formula-first explanation.
Attribution and Review
Published by the Plain Figures editorial team. Review on this site focuses on formula accuracy, assumption clarity, and threshold freshness where current-year rules matter.
MethodologyAuthors and ReviewEditorial Policy
Related Guides

Keep moving through the same topical cluster with nearby explainers that support the calculator.

Read Mortgage Payment Examples: How Rate, Term, and Principal Change the NumberRead Mortgage Rate vs Term: Which Changes the Cost More?Read How Mortgage Affordability Is Assessed
This guide is for general information only. Plain Figures does not provide financial advice. All figures are illustrative. Formulas and tax rules change, so verify current rates and consult a qualified adviser before making decisions.