All calculators

15 vs 30 Year Mortgage Calculator

Compare 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 details

20% of property price
%
Enter the annual interest rate shown in your mortgage illustration or example scenario.
Payment frequency
years
years

The calculator uses the same property price, deposit, interest rate and payment frequency for both illustrations.

Loan amount
£600,000
15-year term estimated payment
£4,823.27per month
30-year term estimated payment
£3,313.22per month
Mortgage term comparison
15 years vs 30 years

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.

Estimated payment, interest and totals for the two mortgage terms compared
Metric15-year term30-year term
Estimated repayment£4,823.27 per month£3,313.22 per month
Payments180 monthly payments360 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
Estimated annual mortgage balance and interest comparison
Year15-year balance30-year balance15-year interest30-year interestBalance 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
16Repaid£393,592Repaid£21,196£393,592
17Repaid£374,031Repaid£20,197£374,031
18Repaid£353,417Repaid£19,145£353,417
19Repaid£331,695Repaid£18,037£331,695
20Repaid£308,805Repaid£16,868£308,805
21Repaid£284,684Repaid£15,637£284,684
22Repaid£259,265Repaid£14,340£259,265
23Repaid£232,479Repaid£12,973£232,479
24Repaid£204,253Repaid£11,532£204,253
25Repaid£174,509Repaid£10,014£174,509
26Repaid£143,165Repaid£8,415£143,165
27Repaid£110,135Repaid£6,729£110,135
28Repaid£75,329Repaid£4,952£75,329
29Repaid£38,651Repaid£3,081£38,651
30Repaid£0Repaid£1,108£0

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.

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.

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.