Mortgage Calculator UK
Repayment and interest-only mortgages
| Month | Payment | Interest | Principal | Remaining |
|---|
Put in the property price, your deposit (in pounds or as a percentage), the interest rate and the term, then choose repayment or interest-only. You’ll see the monthly payment, total interest, total repaid, your loan-to-value and a month-by-month schedule showing how much of each payment is interest.
It’s most useful for comparing options before you talk to a lender or broker: what a bigger deposit does, how much a slightly lower rate saves, or what a 30-year term costs compared with 25.
Monthly payments by loan size
Repayment mortgages at a few example rates. These are illustrations, not current deals, so put your own rate in above.
| Loan | 4% over 25 years | 4.5% over 25 years | 5% over 25 years | 4.5% over 30 years |
|---|---|---|---|---|
| £150,000 | £791.76 | £833.75 | £876.89 | £760.03 |
| £200,000 | £1,055.67 | £1,111.66 | £1,169.18 | £1,013.37 |
| £250,000 | £1,319.59 | £1,389.58 | £1,461.48 | £1,266.71 |
| £300,000 | £1,583.51 | £1,667.50 | £1,753.77 | £1,520.06 |
Half a percentage point matters more than it looks. On £200,000 over 25 years, going from 4% to 4.5% adds about £56 a month and nearly £17,000 in interest over the term.
Three worked examples
A typical purchase. A £300,000 home with a £60,000 (20%) deposit at 5% over 25 years: you borrow £240,000 at 80% LTV, pay £1,403.02 a month and £180,904.83 in interest, £420,904.83 in total.
A first-time buyer with 10% down. A £250,000 home with a £25,000 deposit at 4.5% over 30 years: £225,000 at 90% LTV, £1,140.04 a month, and £185,415.10 of interest. Over 30 years the interest comes to more than the price of a small flat.
Interest-only. A £400,000 property with a £100,000 deposit at 6% over 25 years: £1,500 a month, £450,000 of interest, and the full £300,000 still owed at the end.
25 years or 30?
| £200,000 at 4.5% | Monthly payment | Total interest |
|---|---|---|
| 25 years | £1,111.66 | £133,499 |
| 30 years | £1,013.37 | £164,813 |
The longer term saves about £98 a month but costs about £31,300 more in interest. Plenty of people take the longer term to make the monthly payment manageable, which is reasonable, but it’s worth overpaying when you can to claw back some of that cost. Many lenders now offer 35 years or longer, and the same trade-off gets bigger.
Repayment or interest-only?
With a repayment mortgage, every payment covers the interest and part of the loan, so you owe nothing at the end. With interest-only you just pay the interest, so the monthly cost is lower, but the whole loan is still owed when the term ends. Interest-only is mostly used for buy-to-let. For a home you live in, lenders will usually only agree to it if you can show a credible plan to repay, like investments or selling another property.
How the payment is worked out
For a repayment mortgage the calculator uses M = P × r(1 + r)n ÷ [(1 + r)n − 1], where P is the amount borrowed, r is the annual rate divided by 12, and n is the number of monthly payments. For interest-only it’s simply the loan multiplied by the monthly rate. Loan-to-value is the loan divided by the price; lenders price their deals in LTV bands, often 60%, 75%, 85% and 90%, so a slightly bigger deposit that drops you into a lower band can get you a noticeably better rate.
The calculator assumes one fixed rate for the whole term. Real mortgages usually move to a different rate when the initial deal ends, and lenders may charge fees or work out interest daily, so treat the results as a guide and check the lender’s own illustration.
Overpaying
Overpaying cuts the balance faster, so you pay less interest and finish sooner. Many lenders let you overpay up to 10% of the balance each year during a fixed or tracker deal without an early repayment charge, but check your own terms. For a rough idea of how much extra you’d need, shorten the term in the calculator: the difference between the 25-year and 20-year payments is about what you’d have to add each month.
Checking a remortgage rate
When a fixed or tracker deal ends you’ll usually drop onto the lender’s standard variable rate, which is normally higher. To compare, set the property price to your remaining balance, the deposit to £0, and enter your remaining term and the new rate (ignore the LTV figure). Include arrangement fees and any early repayment charge on your current deal.
Other costs
The mortgage isn’t the only cost of buying. Budget for Stamp Duty in England and Northern Ireland, arrangement, valuation and broker fees, solicitor or conveyancer fees and searches, buildings insurance (lenders require it), moving costs and repairs. It’s also worth testing a rate one or two points higher than today’s to see whether you could cope if rates rise when your deal ends. The Take Home Pay Calculator and Budget Planner help check what you can afford.
Questions people ask
What is the monthly payment on a £200,000 mortgage?
At 4.5% over 25 years, £1,111.66 a month. At 4% it’s £1,055.67 and at 5% it’s £1,169.18.
What is the monthly payment on a £250,000 mortgage?
At 4.5% over 25 years, £1,389.58 a month. Over 30 years at the same rate it’s £1,266.71.
What is the monthly payment on a £300,000 mortgage?
At 4.5% over 25 years, about £1,667.50 a month, with around £200,250 of interest. Over 30 years it falls to £1,520.06.
Is a 25 or 30-year mortgage better?
A 30-year term has lower monthly payments but costs more interest. On £200,000 at 4.5% it saves about £98 a month and adds around £31,300 of interest.
What does LTV mean?
Loan-to-value: the mortgage as a percentage of the property’s value. A £270,000 mortgage on a £300,000 home is 90% LTV. Lower LTVs usually get better rates.
Does the calculator include Stamp Duty or fees?
No, just the mortgage payments and interest. Use the Stamp Duty Calculator for property tax and budget separately for fees and insurance.
Related: Stamp Duty Calculator · Savings Calculator · Compound Interest Calculator
For information only, not financial advice. Speak to a qualified mortgage adviser before you commit. Last reviewed: 3 November 2026.