How to use this calculator
- Enter or choose property price.
- Enter or choose deposit.
- Enter or choose interest rate (per year).
- Enter or choose mortgage term.
- Enter or choose mortgage type.
- The monthly payment updates as you type. Use Copy result or Share to keep it.
Method
Repayment: M = L × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1); Interest-only: M = L × r; LTV = L ÷ Price
- L
- loan = price − deposit
- r
- annual rate ÷ 12 ÷ 100
- n
- term in months
Worked example
- Loan = £300,000 − £30,000 = £270,000, an LTV of 90%.
- r = 4.5 ÷ 12 ÷ 100 = 0.00375 and n = 300; M = 270,000 × 0.00375 × 1.00375³⁰⁰ ÷ (1.00375³⁰⁰ − 1) = £1,500.75.
- At 7.5% (a 3-point rise) the same loan costs £1,995.28 a month.
A £270,000 repayment mortgage at 4.5% over 25 years costs about £1,501 a month, rising to about £1,995 if rates went up by 3 points.
What the result means
Lower LTV bands generally get better rates, so a slightly bigger deposit can cut the cost twice. Most UK deals are fixed for 2–5 years and then revert to a variable rate, which the stress-test figure helps you plan for.
Assumptions and limits
- The rate stays the same for the whole term (in practice it changes when a fixed deal ends).
- Interest is charged monthly at the annual rate ÷ 12.
- Stamp Duty Land Tax, arrangement fees, valuation and legal costs are not included.
- Lenders’ affordability checks are not modelled.
Questions
What is LTV?
Loan-to-value: the mortgage as a percentage of the property price. A £30,000 deposit on £300,000 means a 90% LTV.
Please note: This calculator gives estimates for planning. It is not financial advice, and lenders’ actual terms, fees and rounding may differ.