Mortgage Calculator
Work out the monthly repayment on a level-payment or equal-principal mortgage, the total interest, and how much interest and principal you pay each year.
Monthly payment (first month)
£1,013.37
Level payments
Monthly payment (final month)
£1,013.37
Interest in the first year
£8,934
Total interest
£164,813
Total paid
£364,813
Interest and principal per year
- Interest
- Principal
Show the table
| Year | Interest | Principal |
|---|---|---|
| 1 | £8,934 | £3,226 |
| 2 | £8,786 | £3,375 |
| 3 | £8,631 | £3,530 |
| 4 | £8,469 | £3,692 |
| 5 | £8,299 | £3,861 |
| 6 | £8,122 | £4,039 |
| 7 | £7,936 | £4,224 |
| 8 | £7,742 | £4,418 |
| 9 | £7,539 | £4,621 |
| 10 | £7,327 | £4,834 |
| 11 | £7,105 | £5,056 |
| 12 | £6,872 | £5,288 |
| 13 | £6,629 | £5,531 |
| 14 | £6,375 | £5,785 |
| 15 | £6,110 | £6,051 |
| 16 | £5,832 | £6,329 |
| 17 | £5,541 | £6,620 |
| 18 | £5,237 | £6,924 |
| 19 | £4,919 | £7,242 |
| 20 | £4,586 | £7,574 |
| 21 | £4,238 | £7,922 |
| 22 | £3,874 | £8,286 |
| 23 | £3,493 | £8,667 |
| 24 | £3,095 | £9,065 |
| 25 | £2,679 | £9,482 |
| 26 | £2,243 | £9,917 |
| 27 | £1,788 | £10,373 |
| 28 | £1,311 | £10,849 |
| 29 | £813 | £11,348 |
| 30 | £291 | £11,869 |
Remaining balance by year
- Remaining balance
Show the table
| Year | Remaining balance |
|---|---|
| 0 | £200,000 |
| 1 | £196,774 |
| 2 | £193,399 |
| 3 | £189,869 |
| 4 | £186,177 |
| 5 | £182,316 |
| 6 | £178,277 |
| 7 | £174,053 |
| 8 | £169,634 |
| 9 | £165,013 |
| 10 | £160,179 |
| 11 | £155,123 |
| 12 | £149,835 |
| 13 | £144,304 |
| 14 | £138,519 |
| 15 | £132,468 |
| 16 | £126,139 |
| 17 | £119,519 |
| 18 | £112,596 |
| 19 | £105,354 |
| 20 | £97,779 |
| 21 | £89,857 |
| 22 | £81,571 |
| 23 | £72,904 |
| 24 | £63,838 |
| 25 | £54,357 |
| 26 | £44,439 |
| 27 | £34,066 |
| 28 | £23,217 |
| 29 | £11,869 |
| 30 | £0 |
Total paid, split
- Principal £200,000 54.8%
- Interest £164,813 45.2%
Total £364,813
Please note: This is an example calculation, not financial advice. Personal circumstances, changes in rules and rates, and additional costs are not included. If in doubt, talk to a financial adviser.
Tax relief on mortgage interest, property taxes, insurance, fees and rate changes during the term are not included.
How this number is calculated
The blocks use your input. Change a value above and they update with it.
Step 1 · Number of months
Step 2 · Monthly interest rate
Step 3 · Monthly payment (first month)
Step 4 · Monthly payment (final month)
Step 5 · Total interest
Step 6 · Total paid
How the calculation works
Work out your monthly payment, the total interest and the total amount you pay back. Choose level payments or equal principal and see, year by year, how much of your money goes to interest, how much to principal and how the remaining balance comes down.
A mortgage is repaid in monthly instalments of interest and principal. The interest for a month is the remaining balance times the monthly rate, one twelfth of the annual rate. With level payments (an annuity or repayment mortgage) the payment is the same every month: at the start the balance is high and most of the payment is interest, later more and more goes to principal. With equal principal (a linear mortgage) the same amount is repaid every month, the loan amount divided by the number of months, so the interest and the payment go down a little every month. The calculator uses formulas that give the same result as working through the schedule month by month. Monthly payments are rounded to the penny; totals and yearly amounts to whole units of currency.
Formula
Monthly rate r = annual rate ÷ 12 ÷ 100, number of months n = term × 12. Level payments: payment = loan × r ÷ (1 − (1 + r)^−n), total interest = payment × n − loan. Equal principal: principal per month = loan ÷ n, first payment = loan ÷ n + loan × r, total interest = loan × r × (n + 1) ÷ 2. At 0% interest the payment is loan ÷ n.
Assumptions
- The interest rate stays the same for the whole term; each month is charged one twelfth of the annual rate.
- Each payment is made at the end of the month, with no extra or missed payments.
- Tax relief on mortgage interest and other tax effects are not included: the payment is before tax.
- Property taxes, insurance, mortgage insurance, buying costs and other fees are not included.
- The loan is fully repaid by the end of the term; interest-only parts and balloon payments are not included.
- Monthly payments are rounded to the penny; totals and yearly amounts to whole units of currency.
Example calculations
The button fills in the calculator above, so you can carry on from there.
-
Level payments over 30 years
Monthly payment (first month)
£1,432.25
Loan amount £300,000.00 · Annual interest rate (%) 4 · Term (years) 30 · Level payments
-
Level payments over 20 years
Monthly payment (first month)
£1,449.90
Loan amount £250,000.00 · Annual interest rate (%) 3.5 · Term (years) 20 · Level payments
-
Equal principal over 30 years
Monthly payment (first month)
£2,611.11
Loan amount £400,000.00 · Annual interest rate (%) 4.5 · Term (years) 30 · Equal principal
Frequently asked questions
What is the difference between level payments and equal principal?
With level payments (an annuity or repayment mortgage) the monthly payment is the same every month. With equal principal (a linear mortgage) the same part of the loan is repaid every month, so the payment starts higher and goes down, and the total interest is lower. For 300,000 at 4% over 30 years the total interest is 215,609 with level payments and 180,500 with equal principal.
Why do I repay so little at the start?
Interest is charged on the remaining balance, which is highest at the start. On a level-payment mortgage of 300,000 at 4% over 30 years, 11,904 goes to interest and 5,283 to principal in the first year. In the last year it is 367 interest and 16,820 principal.
Is the monthly payment before or after tax?
Before tax. The calculator shows principal and interest only. Tax relief on mortgage interest, property taxes, insurance and fees are not included, so the amount actually paid each month can be different.
What if the interest rate changes?
The calculator uses one rate for the whole term. In practice a rate is often fixed for a set period and can change after that, and the payment changes with it. Entering a different rate shows the effect on the payment straight away.
Are overpayments included?
No, the calculator follows the regular schedule. An overpayment lowers the remaining balance and with it the interest charged afterwards. How much can be overpaid without an early repayment charge depends on the terms of the loan.
How exact is the result?
The result is the same as working through the schedule month by month, with monthly payments rounded to the penny and totals to whole units. Lenders may round differently or charge interest per day, so their figures can differ slightly.
Sources and checks
Sources
- UK House Price Index for July 2026 | GOV.UK (opens in a new tab)
- Money and Credit - August 2026 | Bank of England (opens in a new tab)
How we check it
This calculator has 21 fixed checks: 13 calculations with a result that is fixed in advance, and 8 cases of invalid input that must be rejected. They all run automatically every time we publish; if one fails, the calculator does not go live.
See the calculations
- Loan amount £300,000.00 · Annual interest rate (%) 4 · Term (years) 30 · Level payments → Monthly payment (first month) £1,432.25
- Loan amount £300,000.00 · Annual interest rate (%) 4 · Term (years) 30 · Equal principal → Monthly payment (first month) £1,833.33
- Loan amount £250,000.00 · Annual interest rate (%) 3.5 · Term (years) 20 · Level payments → Monthly payment (first month) £1,449.90
- Loan amount £400,000.00 · Annual interest rate (%) 4.5 · Term (years) 30 · Equal principal → Monthly payment (first month) £2,611.11
- Loan amount £120,000.00 · Annual interest rate (%) 0 · Term (years) 10 · Level payments → Monthly payment (first month) £1,000.00
- Loan amount £120,000.00 · Annual interest rate (%) 0 · Term (years) 10 · Equal principal → Monthly payment (first month) £1,000.00
- Loan amount £12,000.00 · Annual interest rate (%) 6 · Term (years) 1 · Level payments → Monthly payment (first month) £1,032.80
- Loan amount £2,000,000.00 · Annual interest rate (%) 15 · Term (years) 40 · Level payments → Monthly payment (first month) £25,064.48
- Loan amount £2,000,000.00 · Annual interest rate (%) 15 · Term (years) 40 · Equal principal → Monthly payment (first month) £29,166.67
- Loan amount £200,619.00 · Annual interest rate (%) 4 · Term (years) 30 · Equal principal → Monthly payment (first month) £1,226.01
Changes
- : Separate default loan amounts and interest rates for the UK and the US, with official sources for both.
- : Clearer help texts for the fields. Sources added and content reviewed.
- : First version.
Last reviewed: · How we build and check our calculators
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