Mortgage calculator: monthly repayments

Amount, rate, term and insurance: see the monthly payment, what the loan costs in total and how the balance falls year by year. No form, no call back.

Your monthly payment, insurance included

£1,512.40

of which £1,449.90 loan and £62.50 insurance, over 240 months

Total cost of credit: £112,975.83
of which interest: £97,975.83
of which insurance: £15,000.00
Total repaid: £362,975.83

Capital 69%Cost of credit 31%

How we calculated it

M = C × i ÷ [1 − (1 + i)⁻ⁿ]

C = £250,000, i = 3.5% ÷ 12 = 0.2917%, n = 240 months → £1,449.90 before insurance

Estimate only: arrangement, valuation and broker fees are not included, and the nominal rate is not the APRC.

Amortisation table by year

Year	Capital repaid	Interest paid	Balance outstanding
1	£8,788.89	£8,609.90	£241,211.11
2	£9,101.48	£8,297.31	£232,109.63
3	£9,425.20	£7,973.60	£222,684.43
4	£9,760.42	£7,638.37	£212,924.01
5	£10,107.57	£7,291.22	£202,816.44
6	£10,467.07	£6,931.73	£192,349.37
7	£10,839.35	£6,559.44	£181,510.02
8	£11,224.87	£6,173.92	£170,285.15
9	£11,624.10	£5,774.69	£158,661.05
10	£12,037.54	£5,361.25	£146,623.51
11	£12,465.68	£4,933.11	£134,157.83
12	£12,909.04	£4,489.75	£121,248.79
13	£13,368.18	£4,030.61	£107,880.61
14	£13,843.64	£3,555.15	£94,036.97
15	£14,336.02	£3,062.77	£79,700.95
16	£14,845.91	£2,552.88	£64,855.04
17	£15,373.93	£2,024.86	£49,481.11
18	£15,920.74	£1,478.06	£33,560.37
19	£16,486.99	£911.80	£17,073.38
20	£17,073.38	£325.41	£0.00

A lender sums an offer up in three numbers: the monthly payment, the term and the rate. This page rebuilds the rest from four entries, the amount borrowed, the annual rate, the term in years and the insurance rate, and returns the monthly payment with cover included, the total cost of the credit and the total amount repaid.

The amortisation schedule, folded away beneath the results, breaks each year down into principal repaid, interest paid and balance outstanding, and a button exports it as a CSV file for a spreadsheet. The figures you type stay in the tab: no form is submitted and nothing is passed to a lender or a broker.

The model is a plain fixed-rate loan with constant monthly payments. It does not reproduce an offer: several real costs are missing from it, and they are listed below so the gap with the true cost stays visible. The formula, the split between interest and principal and the insurance premium are set out with the figures from the default simulation, 250,000 over twenty years, so the result can be checked line by line.

How to use it

Enter the amount borrowedThis is the sum the lender advances once your deposit has been taken off, not the price of the property and not the total budget for the move. The field opens on 250,000.
Enter the annual rateSet in steps of 0.01, this is the nominal rate of the loan, the one the interest is calculated from. It is not the all-in annual rate printed on the formal offer.
Choose the termFrom 1 to 35 years. Stretching the term lowers the monthly payment and raises the total interest paid; both effects show up in the result boxes as soon as the figure changes.
Set the insurance rateExpressed as an annual percentage of the amount borrowed, in steps of 0.05. Put it at zero to isolate the loan itself and see exactly what the cover adds to the monthly payment.
Open the schedule and export itThe amortisation table by year unfolds under the results. The export button below it writes a file named amortissement.csv, semicolon separated, which a spreadsheet opens directly.

The constant payment formula

The payment before insurance follows a single formula: M = C × i ÷ [1 - (1 + i)^(-n)], where C is the capital borrowed, n the number of monthly payments and i the monthly rate. Here the monthly rate is the annual rate divided by twelve, the proportional convention used in credit contracts rather than the twelfth root used for savings products. If the rate is zero, the page simply divides the capital by the number of months.

With the default values, 250,000 over twenty years at 3.5 percent, the monthly rate is 0.2916667 percent, there are 240 payments, and the payment before insurance comes out at 1,449.90. Cover at 0.3 percent a year of the amount borrowed adds 250,000 × 0.003 ÷ 12 = 62.50 a month. The payment displayed is therefore 1,512.40, for a total repaid of 362,975.83 and a total cost of credit of 112,975.83, made up of 97,975.83 in interest and 15,000 in premiums.

The result boxes carry a pound sign, but nothing in the model depends on the currency: the formula is the same in pounds or dollars, only the surrounding rules differ.

What the schedule shows

Each payment splits into interest, calculated on the balance still outstanding, and a repayment of principal that absorbs whatever is left. As the balance falls the interest share shrinks and the principal share grows, while the payment itself never moves. On the example above, the first payment carries 729.17 of interest against 720.73 of principal; a full year later the balance has only come down to 241,211.11.

Halfway through the term, after ten years, 146,623.51 is still owed: barely more than 41 percent of the capital has been cleared even though half the payments have been made. The final year is the mirror image, 17,073.38 of principal against 325.41 of interest. That imbalance explains why selling early costs more than the headline rate suggests.

The schedule works from the payment excluding insurance, because the premium repays no capital and generates no interest; it stays visible in the total cost of credit, where it weighs 15,000 here. The exported CSV repeats the four annual columns, with a decimal point and a byte order mark so that accented column headings display correctly in a spreadsheet.

What this calculation leaves out

Arrangement and booking fees, the cost of the lender's security, whether a mortgage charge, a guarantee or a surety, broker commission and the legal costs of the purchase all sit outside the calculation. So do the taxes on the transaction, often the largest single line: stamp duty in England, or transfer duties in France, where those costs together run to roughly seven to eight percent of the price on an existing home and markedly less on a new build.

Also absent are interest charged during a construction period before repayments begin, deferred amortisation, payment holidays, adjustable payments and early repayment charges. Those charges are capped in some jurisdictions: in France they cannot exceed the lower of six months of interest on the capital repaid and 3 percent of the balance outstanding. Elsewhere the contract sets them.

The insurance is finally modelled as a level premium based on the original amount borrowed, which is how a lender's group policy usually works. A policy priced on the outstanding balance produces a premium that falls year after year, so the figure shown here is an upper bound rather than a prediction.

The real terms are not decided here

A rate depends on the borrower's profile, the deposit, the loan-to-value ratio and the lender's appetite that month. The rate typed above is the nominal one. The figure that lets two offers be compared is the all-in annual rate regulators require on the formal document: the APRC in the United Kingdom and the European Union, the APR in the United States, the TAEG in France. It folds in compulsory cover and fees, so it always sits above the nominal rate.

Lending is constrained on the other side too. Affordability tests, caps on the share of income a payment may absorb and limits on the term vary by country and change over time: in France the financial stability authority sets a debt service ratio of 35 percent of income including insurance and a maximum term of twenty-five years. Borrowers can often buy the insurance cover somewhere other than the lending bank, provided the guarantees are equivalent.

This page produces arithmetic, not an offer. It cannot say whether a project is financeable, it knows nothing about your income or your other commitments, and it is not financial advice.

Frequently asked questions

Do I enter the price of the property or the amount borrowed?

The amount borrowed. Take your deposit off the total budget, and add back whatever share of the associated fees the lender agrees to finance. Entering the purchase price overstates both the payment and the total cost.

Is the rate asked for the APR?

No, it is the nominal rate. The all-in annual rate adds compulsory insurance, arrangement fees and the cost of the lender's security on top. It is the figure printed on the formal offer, and the only one that makes two proposals comparable.

Why does the insurance not appear in the schedule?

Because it repays no capital and generates no interest. It is added to the monthly payment but stays outside the amortisation, which is why the table works from the payment excluding cover. Its weight shows up in the total cost of credit, 15,000 on the default simulation.

What does adding five years to the term cost?

On the default simulation, moving from twenty to twenty-five years brings the monthly payment down from 1,512.40 to 1,314.06, but raises the total cost from 112,975.83 to 144,217.68. That is 31,241.85 more paid in exchange for a payment 198.34 lighter.

Can I simulate an overpayment or a stepped loan?

No. The model assumes a constant payment at a fixed rate, with no deferral, no modulation and no second loan running alongside. A subsidised or interest-free loan has to be calculated separately and the two payments added together.

What exactly is in the exported file?

A CSV named amortissement.csv, semicolon separated, with one row per year: year number, principal repaid, interest paid and balance outstanding, each rounded to the cent. It carries a byte order mark so a spreadsheet reads the accented headings correctly.