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15 vs 30 Year Mortgage Calculator
Sign up to favourite this calculatorCompare two repayment mortgage terms using the same loan amount and interest rate. The default comparison is 15 years versus 30 years, but you can enter any two whole-year terms.
Mortgage term comparison
The 15-year term has a higher estimated payment and a lower estimated total interest figure. The 30-year term has a lower estimated payment and a higher estimated total interest figure, using the same interest rate in this illustration.
Estimated payment: £1,510.04 more per month with the 15-year term.
Estimated total interest: £324,572 less over the illustrated terms with the 15-year term.
| Metric | 15-year term | 30-year term |
|---|---|---|
| Estimated repayment | £4,823.27 per month | £3,313.22 per month |
| Payments | 180 monthly payments | 360 monthly payments |
| Estimated total interest | £268,188 | £592,760 |
| Estimated total repaid | £868,188 | £1,192,760 |
| Loan balance after 5 years | £449,547 | £552,897 |
| Year | 15-year balance | 30-year balance | 15-year interest | 30-year interest | Balance difference |
|---|---|---|---|---|---|
| 1 | £572,977 | £591,540 | £30,856 | £31,298 | £18,563 |
| 2 | £544,500 | £582,624 | £29,403 | £30,843 | £38,124 |
| 3 | £514,492 | £573,230 | £27,871 | £30,364 | £58,738 |
| 4 | £482,870 | £563,329 | £26,257 | £29,859 | £80,460 |
| 5 | £449,547 | £552,897 | £24,556 | £29,326 | £103,350 |
| 6 | £414,432 | £541,903 | £22,764 | £28,765 | £127,471 |
| 7 | £377,429 | £530,318 | £20,876 | £28,174 | £152,890 |
| 8 | £338,435 | £518,111 | £18,886 | £27,551 | £179,676 |
| 9 | £297,344 | £505,246 | £16,788 | £26,894 | £207,902 |
| 10 | £254,044 | £491,690 | £14,579 | £26,202 | £237,646 |
| 11 | £208,414 | £477,404 | £12,250 | £25,473 | £268,990 |
| 12 | £160,331 | £462,350 | £9,796 | £24,705 | £302,020 |
| 13 | £109,661 | £446,487 | £7,210 | £23,895 | £336,826 |
| 14 | £56,266 | £429,771 | £4,485 | £23,042 | £373,504 |
| 15 | £0 | £412,155 | £1,613 | £22,143 | £412,155 |
| 16 | Repaid | £393,592 | Repaid | £21,196 | £393,592 |
| 17 | Repaid | £374,031 | Repaid | £20,197 | £374,031 |
| 18 | Repaid | £353,417 | Repaid | £19,145 | £353,417 |
| 19 | Repaid | £331,695 | Repaid | £18,037 | £331,695 |
| 20 | Repaid | £308,805 | Repaid | £16,868 | £308,805 |
| 21 | Repaid | £284,684 | Repaid | £15,637 | £284,684 |
| 22 | Repaid | £259,265 | Repaid | £14,340 | £259,265 |
| 23 | Repaid | £232,479 | Repaid | £12,973 | £232,479 |
| 24 | Repaid | £204,253 | Repaid | £11,532 | £204,253 |
| 25 | Repaid | £174,509 | Repaid | £10,014 | £174,509 |
| 26 | Repaid | £143,165 | Repaid | £8,415 | £143,165 |
| 27 | Repaid | £110,135 | Repaid | £6,729 | £110,135 |
| 28 | Repaid | £75,329 | Repaid | £4,952 | £75,329 |
| 29 | Repaid | £38,651 | Repaid | £3,081 | £38,651 |
| 30 | Repaid | £0 | Repaid | £1,108 | £0 |
Estimated mortgage balance by term
The dark line shows the first mortgage term and the orange line shows the second term, using the same loan amount and assumed interest rate.
For exact annual figures, view the Breakdown tab.
| Metric | 15-year term | 30-year term |
|---|---|---|
| Estimated repayment | £4,823.27 per month | £3,313.22 per month |
| Payments | 180 monthly payments | 360 monthly payments |
| Estimated total interest | £268,188 | £592,760 |
| Estimated total repaid | £868,188 | £1,192,760 |
| Loan balance after 5 years | £449,547 | £552,897 |
Assumptions used
- Same property price and deposit for both illustrations
- Same loan amount: £600,000
- Constant annual interest rate: 5.25%
- Payment frequency: monthly
- First mortgage term: 15 years
- Second mortgage term: 30 years
- No mortgage product fees, arrangement fees, valuation or legal costs, insurance, taxes, early-repayment charges, overpayments, payment holidays, rate changes or lender-specific rules included
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Assumptions and limits
- An estimate from the numbers you entered, for guidance only. It is not financial, tax or medical advice.
- Calculator version 1, last updated 25 October 2026.
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How to use this calculator
Pick your currency, then enter the property price, your deposit, the annual interest rate and the payment frequency. Enter the two mortgage terms you want to compare in whole years — 15 and 30 by default. The calculator subtracts the deposit from the price to get the loan amount, then builds a separate repayment schedule for each term using the same loan amount, rate and frequency.
The result shows the estimated payment, number of payments, total interest and total repaid for each term side by side, along with the difference in payment and in total interest. The Breakdown tab lists the annual balance and interest for both schedules, the Chart tab plots the two balance paths, and the Summary tab lists the assumptions used.
This is a neutral illustration of the arithmetic trade-off, not mortgage advice. It does not assess affordability, provide a lender quote, check eligibility, forecast interest rates or recommend one term over another.
What do I need to enter?
- Property price — what the home costs, before any deposit. Must be above zero and at most 100,000,000.
- Deposit — the cash you put in. The loan is the price minus this, so it must be zero or more and below the price.
- Annual interest rate — the yearly rate, 0% to 100%, held fixed for both terms.
- Payment frequency — Monthly (12 payments a year) or Yearly (one).
- First mortgage term and Second mortgage term — the two terms to compare, each a whole number of years from 1 to 50. They must be different.
What do the results show?
- Mortgage term comparison — the two terms being compared, with a summary of the payment and interest differences between them.
- Estimated repayment and Payments — the level payment for each term and how many payments it takes.
- Estimated total interest and Estimated total repaid — what each term costs in interest, and the sum of every payment.
- Loan balance after 5 years — what is still owed at the five-year mark, shown when either term is five years or longer.
- Breakdown, Chart and Summary tabs — the year-by-year balance and interest for both terms, a line chart of the two balances, and the assumptions used.
How mortgage terms are compared
The calculator works out the loan amount by subtracting the deposit from the property price. It then creates two repayment schedules using the same interest rate and payment frequency, with a separate calculated repayment amount for each mortgage term.
- P — loan amount, the property price minus the deposit
- r — the annual interest rate you enter, as a decimal (5.25% is 0.0525)
- m — payments per year: 12 for monthly, 1 for yearly
- i = r ÷ m — the periodic interest rate
- TA, TB — the first and second mortgage terms in whole years
- nA = TA × m, nB = TB × m — the number of payments for each term
- MA, MB — the level periodic repayment for each term
- Bt — the balance remaining at the end of period t, starting from B0 = P
M = P × i(1 + i)ⁿ ÷ ((1 + i)ⁿ − 1)
- P = property price − deposit
- i = r ÷ m
- nA = TA × m, nB = TB × m
- Apply the formula once with nA for MA and once with nB for MB
- If r = 0, MA = P ÷ nA and MB = P ÷ nB
Bt = Bt−1 − (paymentt − interestt)
- interestt = Bt−1 × i
- paymentt = min(M, Bt−1 + interestt)
- The final payment is capped so the balance cannot fall below zero
For each period, interest is charged on the outstanding balance and the rest of the payment clears capital. The annual figures shown in the table and chart are the raw period-level results aggregated into schedule years. Total interest is the sum of every period's interest charge, and total repaid is the sum of every payment.
The shorter term generally produces a higher periodic repayment and lower total interest in this constant-rate illustration. The longer term generally produces a lower periodic repayment and higher total interest. Actual payments, costs and lender terms can differ.
Selecting a currency changes labels and number formatting only. It does not convert amounts using exchange rates.
A worked 15 vs 30 year example
Take a £750,000 property with a £150,000 deposit, so the loan amount P is £600,000, at a 5.25% annual rate with monthly payments (m = 12, i = 0.0525 ÷ 12).
- 15-year term: nA = 15 × 12 = 180 payments. Applying the payment formula gives an estimated repayment of about £4,824 per month.
- 30-year term: nB = 30 × 12 = 360 payments. The same formula gives an estimated repayment of about £3,313 per month.
The 15-year term costs roughly £1,511 more each month but clears the loan in half the time and accrues far less total interest — around £268,000 versus about £593,000 over the illustrated terms. Enter your own figures above to see the comparison for your scenario.
Other ways to pay off a mortgage faster
Choosing a shorter term outright is one way to clear a mortgage sooner. The Mortgage Calculator with Extra Payments models keeping the longer term and adding a regular or one-off overpayment instead, and the Biweekly Mortgage Calculator models a schedule of half-payments every two weeks.
Frequently asked questions
What does this calculator compare?
It compares two repayment mortgages that share the same property price, deposit, interest rate and payment frequency but run over different whole-year terms. The default comparison is 15 years versus 30 years. For each term it works out the level payment, the number of payments, the total interest, the total repaid and the balance over time, then shows the arithmetic difference between the two. It is a neutral illustration of the trade-off, not mortgage advice, an affordability check, a lender quote or a recommendation of one term over another.
Can I enter terms other than 15 and 30 years?
Yes. The two term fields accept any whole number of years from 1 to 50, and the two terms just have to be different from each other. Enter 20 and 25, or 10 and 30, or any other pair. Every figure, table, chart and label updates from the terms you enter.
Why does a shorter mortgage term usually have a higher payment?
The same loan amount has to be cleared in fewer payments, so each payment must be larger. A 15-year term at monthly payments has 180 payments to repay the loan; a 30-year term has 360. Spreading the same balance across half as many payments raises each one, even though the shorter term charges less interest in total.
Why does a longer term usually have more total interest?
Interest is charged on the outstanding balance every period. A longer term keeps a larger balance outstanding for longer, so more interest accrues before the loan is cleared, even though each payment is smaller. At a 0% interest rate both terms have no interest and the only difference is the payment size.
What happens if I enter two terms in a different order?
The order does not change the maths. The calculator reads the raw term values, works out which is shorter and which is longer, and phrases every comparison accordingly. Entering 30 then 15 gives the same comparison as 15 then 30, with the column order following what you typed.
Why might my lender’s figures differ?
The calculator uses one constant interest rate for the whole term and a simple nominal periodic rate. Real lenders use their own day-count and rounding conventions, may calculate interest daily or monthly, apply payments on set dates, and charge fees the illustration excludes. Your rate is also likely to change when a fixed, tracker or discounted period ends. Treat the output as an illustration of the arithmetic, not a statement of what your lender will do.
Are overpayments, fees and rate changes included?
No. The illustration excludes arrangement and product fees, valuation and legal costs, insurance, taxes, early-repayment charges, overpayments, payment holidays, offset features, rate changes and lender-specific rules. It models a plain repayment mortgage with the entered rate held constant and every payment made on schedule.
Does changing currency convert the mortgage amount?
No. Selecting a currency changes the currency symbol and number formatting on every field and result and nothing else. The property price, deposit, loan amount, payments, schedules and totals keep the same nominal numbers — 600,000 stays 600,000 whether it is shown as pounds, dollars or euros. There is no exchange-rate conversion.
Last updated 25 October 2026.