THE NUMBERS, EXPLAINED
How to use this calculator.
Simple fee recovery compares payment savings only. A longer replacement term can cost more overall even with lower payments; compare full repayment totals separately.
Start with your inputs
Enter existing balance (£), old annual rate (%), old months remaining, new rate (%), new term months, refinance fees (£). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Existing balance (£) | 10000 |
| Old annual rate (%) | 8 |
| Old months remaining | 60 |
| New rate (%) | 5 |
| New term months | 60 |
| Refinance fees (£) | 500 |
A worked example
With the example inputs above, monthly saving (£) is 14.05. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Monthly saving (£) | 14.05 |
| Simple fee recovery (months) | 35.58312 |
How this is calculated
Monthly saving (£)
monthlyPayment(a, b, c) − monthlyPayment(a, d, e), using the definition below.
Simple fee recovery (months)
If the monthly saving is positive: f / monthly saving. Otherwise report no monthly saving.
Symbols and units
- a
- Existing balance (£)
- b
- Old annual rate (%)
- c
- Old months remaining
- d
- New rate (%)
- e
- New term months
- f
- Refinance fees (£)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Calculation steps and notation
monthlyPayment(P, R, n): P is principal, R the nominal annual percentage and n monthly payments. Let q = R/1200. Payment = P × q / (1 − (1+q)^(−n)). If q = 0, payment = P/n.
Assumptions and limits
Simple fee recovery compares payment savings only. A longer replacement term can cost more overall even with lower payments; compare full repayment totals separately.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Monthly saving (£); Simple fee recovery (months). The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Simple fee recovery compares payment savings only. A longer replacement term can cost more overall even with lower payments; compare full repayment totals separately.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →