Interest Saved
$38,266.59
New Monthly
$1,375.77 vs Old: $1,228.17
Rates & sources
Standard amortisation formulas used across UK lenders. Interest rates move daily — confirm with your lender or broker.
Source: Bank of England — Statistics — figures refreshed at the start of each tax year.
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
A realistic US planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Loan Amount ($)
$280,000
Interest Rate (%)
5%
Original Term (Years)
25 years
New Term (Years)
25 years
After entering these figures, review interest saved and new monthly together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Interest Saved
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
New Monthly
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator models the effect of making one or more overpayments on a standard capital repayment mortgage. It recalculates the full amortisation schedule from the point of each overpayment, showing how the reduction in principal leads to lower interest charges in every subsequent month. The interest saving figure represents the cumulative difference between the original schedule and the revised one. The calculation assumes the interest rate remains constant throughout the remaining term, which will not be the case if you are on a tracker or variable rate product. It also assumes the lender applies the overpayment immediately to the principal rather than holding it in a suspense account — practices vary, so confirm the arrangement with your lender.
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes, or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures and total costs.
- !Not accounting for the impact of a rate revert after an introductory fixed period ends, which can sharply increase payments.
What to do next
- Run a second scenario with a higher rate or shorter term so you can see the downside clearly.
- Compare the result with an affordability or overpayment calculator before applying.
- Use the related guides below to understand trade-offs before you request live quotes.
- Note down the monthly payment and total interest for your two or three strongest scenarios so you have a clear comparison ready when you speak to a broker.
- Check whether making a modest overpayment each month would reduce total interest significantly — run the overpayment calculator next to find out.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
Where to go after this calculator
Move to a focused hub instead of restarting your research from scratch.
Best Tools for Small Business
Pick software, validate unit economics, and execute workflows with one connected path.
Open hub →
Startup Resource Center
A startup stack for software decisions, runway math, and practical launch workflows.
Open hub →
Creator Toolkit
Choose creator platforms, calculate revenue targets, and ship assets faster.
Open hub →
Money Management Tools
A practical path for financial product choices, scenario math, and planning utilities.
Open hub →