Useful next calculations
When to use this calculator
- Before comparing mortgage products, brokers or repayment types.
- When you want to test how a different deposit, rate or term changes the payment.
- When you need a quick estimate before using a formal illustration or agreement in principle.
- When you are stress-testing your budget against a higher rate.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Mortgage balance (£) | £200,000 |
| Mortgage rate (%) | 4.75% |
| Extra monthly amount (£) | £200 |
For those figures the calculator returns:
- Illustrative first-year interest: £9,500.00
- Extra monthly amount: £200.00
Method & assumptions
This planner compares two uses for the same monthly cash: reducing a repayment mortgage balance or accumulating a savings pot. It models fixed entered rates, a chosen comparison period and a one-off early repayment charge, then keeps the mortgage balance and savings value visible side by side.
It also shows the estimated LTV after overpayments and the further amount required to reach a selected milestone. LTV milestones are not promises of a lender rate or acceptance.
The result does not include tax unless you enter a net savings rate, investment returns, offset mortgages, changing rates, annual lender overpayment caps or the value of accessible emergency cash. Check the lender illustration and account terms before acting.
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.
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.
- Note the monthly payment and total interest for your strongest scenarios before you speak to a broker.
- Check whether a modest overpayment would reduce total interest — use the overpayment calculator next.