Whether you’re buying your first home, remortgaging, or just trying to work out what a rate rise will do to your monthly budget, these calculators will give you an instant answer.
No sign-up, no data collected — just plug in your numbers and go.
Monthly Repayment Calculator
Work out exactly what your monthly mortgage payment will be based on your loan amount, term, and interest rate.
Rate Change Comparison
Remortgaging or worried about your rate going up? Enter your current deal and the new one to see exactly how much more (or less) you will pay each month.
Current Mortgage
New Mortgage
A few things worth knowing
These figures are estimates. The calculators use a standard capital repayment formula, which is what most UK residential mortgages use. Interest-only mortgages work differently — your monthly payment would just be the interest portion, with the full loan still owed at the end.
The rate you see advertised is not always the rate you pay. Lenders quote an initial rate (e.g. a two-year fix) but the APRC (Annual Percentage Rate of Charge) is the better number to compare across deals — it includes fees spread over the full term.
Overpaying can save you thousands. Most UK mortgages allow you to overpay by up to 10% per year without penalty. Even a small regular overpayment reduces the total interest significantly over a 25-year term.
Always speak to a broker. A fee-free mortgage broker has access to deals you won’t find on comparison sites and can advise on the right product for your circumstances. This calculator is a starting point, not financial advice.
How I Use This Calculator
The most useful way to use a mortgage calculator is not to enter one perfect number and call it done. I prefer to run three versions: the deal I hope to get, a realistic middle case, and an uncomfortable-but-possible rate. That gives you a much clearer sense of whether the monthly payment is genuinely affordable or only affordable if everything goes perfectly.
For example, on a £250,000 repayment mortgage over 25 years, a move from 4.5% to 5.5% is not a neat little rounding error. It changes the monthly bill by enough to affect the rest of the household budget. That is the bit people often miss when they focus only on the house price or deposit. The monthly payment is the thing you actually have to live with.
Do Not Forget the Boring Costs
The calculator only covers the mortgage repayment. It does not include buildings insurance, life insurance, council tax, service charges, ground rent, maintenance, moving costs, furniture, repairs, or the sudden discovery that every room needs curtains and every curtain rail costs more than it morally should.
If you are moving from renting to owning, build a separate monthly line for maintenance. A simple starting point is to set aside something every month even if you do not spend it immediately. Houses have a habit of saving up their problems and presenting them as a single expensive weekend.
What to Check Before Comparing Deals
When comparing two mortgage deals, look beyond the headline rate. Product fees can change the real cost, especially on smaller mortgages. A slightly higher rate with no fee can sometimes beat a lower-rate deal with a large upfront fee. The calculator gives you the monthly repayment, but you still need to add the fees into the full comparison.
Also check the loan-to-value band. A bigger deposit can move you into a better rate bracket, but only if it crosses a lender’s threshold. Going from a 91% mortgage to 90% can matter. Going from 88% to 87% may not change much at all. A broker can tell you where those breakpoints are for the deals currently available to you.
Stress-Test the Family Budget
Before committing, I would test the payment against real life rather than against an ideal spreadsheet. Could you still manage it if childcare costs rose, one car needed replacing, energy bills jumped, or one income dipped for a few months? If the answer is only “yes” when every other category is squeezed to nothing, the mortgage may be technically approved but still too tight.
That does not mean you should be scared off buying. It just means the safe number is the one that leaves space for normal family chaos. A mortgage should fit around your life, not require your life to behave perfectly for 25 years.
This tool is provided for illustrative purposes only and does not constitute financial advice. Always consult a qualified mortgage adviser before making any decisions.
