Example result based on the prefilled values.
Estimated Saving Over Deal Period
£8,105.84
Current Monthly Payment
£1,375.77
New Monthly Payment
£1,265.30
Switching Break-even
10 months
New Balance at Comparison End
£165,399.98
New Interest + Switching Costs
£42,816.91
Continue your plan
Useful next calculations
Rates & sources
Illustrative comparison using the rates, remaining term, deal period, fees, cashback and early repayment charge entered. Product fees added to the mortgage increase the balance and accrue interest.
Source: MoneyHelper — remortgaging to cut costs — check the linked guidance and any live quote before acting.
When to use this calculator
- Before buying, renting, refinancing, or reviewing a property investment.
- When you want to compare cash flow, yield, growth, and ownership costs side by side.
- When you need a fast estimate before speaking to an agent, lender, or adviser.
- When you are assessing whether a rental property still makes financial sense after a mortgage rate change.
- When you want to compare the total cost of renting against owning over a five- or ten-year horizon.
A realistic UK planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Mortgage balance (£)
£200,000
Remaining mortgage term (years)
£200,000
Compare costs over (years)
25 years
Current mortgage rate (%)
£200,000
After entering these figures, review estimated saving over deal period, current monthly payment and new monthly payment 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
Estimated Saving Over Deal Period
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.
Current Monthly Payment
Use this to check whether the scenario fits comfortably within your regular budget. If it looks tight, rerun the tool with a longer term or larger deposit to find the boundary of affordability.
New Monthly Payment
Use this to check whether the scenario fits comfortably within your regular budget. If it looks tight, rerun the tool with a longer term or larger deposit to find the boundary of affordability.
Switching Break-even
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 Balance at Comparison End
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 Interest + Switching Costs
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 UK remortgage comparison estimates the cost of staying on the current mortgage against moving to a new deal for the period you choose. It calculates the payment and interest for each option, then adds the new product fee, legal and valuation costs, current-lender exit charges or ERCs, and subtracts genuine cashback.
If you add the product fee to the mortgage, the tool increases the new opening balance and charges interest on that larger balance. The fee itself also remains a cost. The break-even month is the first month when the estimated cumulative interest saving has recovered the net switching costs.
Rates are held constant for the comparison and every fee is user-entered. The result does not model future product changes, lender underwriting, affordability, porting, repayment-charge bands, tax, offset balances or product-specific conditions. Confirm the figures in the lender's personalised illustration and seek regulated advice where appropriate.
Common mistakes
- !Comparing rent and ownership costs without including taxes, fees, and maintenance.
- !Using purchase price alone without testing the impact of financing or vacancy assumptions.
- !Relying on yield or growth in isolation instead of reviewing the full property case.
- !Forgetting Stamp Duty Land Tax (or its Scottish and Welsh equivalents), which can add thousands to the true cost of purchase.
- !Using optimistic rental growth figures without also testing a flat or declining rent scenario to check downside resilience.
What to do next
- Run a second scenario with a higher rate or lower rental yield to check downside resilience.
- Compare the result with a buy-versus-rent or stamp duty calculator before making an offer.
- Use the related guides below to understand agent fees, legal costs, and ongoing maintenance budgets.
- If you are assessing a buy-to-let, check the gross yield against the net yield after mortgage interest, voids, and management fees.
- Note down the key figures from this scenario to share with your solicitor or mortgage broker so they are working from the same assumptions.
Frequently asked
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