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Mortgage calculator

Price, deposit, rate, term: the monthly payment, the total interest, and the year-by-year path back to owning the whole thing.

Guide

How to use it

  1. Enter the property price and your deposit, the difference is what you borrow.
  2. Enter the interest rate. Use the rate itself for a fix you are considering, today’s typical fixes sit in the 4s, your actual offer depends on deposit size and credit.
  3. Set the term. 25 years is traditional, longer terms cut the monthly cost but grow the total interest markedly.
  4. Read the monthly payment and open the year-by-year table, the early years are mostly interest, which is normal and temporary.
  5. Toggle interest-only to see that comparison, and what it leaves unpaid.

Examples

The trade-offs, in numbers

£255K AT 4.5%

A £285,000 home with £30,000 down over 25 years: about £1,417 a month, and roughly £170,000 of interest across the term. The default example in the tool, adjust from there.

25y → 35y

Stretching the same loan to 35 years drops the monthly by around £210 but adds roughly £80,000 of interest. Longer terms are a cash-flow tool with a real price tag.

5% → 10% DEPOSIT

Doubling a small deposit does two things: borrows less, and unlocks cheaper rate brackets (loan-to-value bands at 90%, 85%, 80%). The second effect often matters more than the first.

Method

How it works

The monthly payment uses the standard amortisation formula: the payment that exactly clears the balance, with interest accruing monthly, over the chosen term. The year table applies each payment month by month, splitting it into interest (balance × monthly rate) and repayment (the rest).

Interest-only mode divides the annual interest by twelve and leaves the balance untouched, honest about what that means at term end. Fees, rate changes after a fixed period and insurance are deliberately out of scope, they belong in a broker conversation.

FAQ

Frequently asked questions

How much deposit do I need?

5% is the practical minimum for mainstream lending, 10% opens better rates and 25% the best. Loan-to-value bands are the rate card’s skeleton.

Repayment or interest-only?

Repayment unless you have a genuine repayment vehicle: interest-only leaves the whole loan due at term end, and lenders now demand evidence of the plan. The toggle shows both honestly.

What rate should I type in?

The rate of the product you are actually considering, or a mid-4s placeholder for rough planning. Your offer depends on LTV and credit file, not the advertised best-buy.

Why is so much of my early payment interest?

Interest is charged on the outstanding balance, which is biggest at the start. The table shows the crossover, typically a third of the way in, after which repayment dominates.

Does this include stamp duty and fees?

No, this is the loan itself. The stamp duty calculator handles that cost, and product fees vary by deal.

Is this advice?

No, arithmetic. Affordability, product choice and stress tests are a regulated broker’s or lender’s job.

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Mortgage overpaymentWhat £100 extra a month actually saves. How much can I borrow?Income multiples, with the caveats. Stamp duty calculatorThe tax on top of the price. Take-home payWhat is left to pay it with.
Skip to the tool

Mortgage calculator

Price, deposit, rate, term: the monthly payment, the total interest, and the year-by-year path back to owning the whole thing.

£1,417 repayment, per month
£255,000 amount borrowed (11% deposit)
£170,212 total interest over the term

Formula: monthly rate 0.375% on £255,000 across 300 payments. Early payments are mostly interest, the year-by-year table shows the balance bending downwards faster as the years pass.

Year by year
YearBalanceInterestRepaidRemaining 1 £11,359 £5,649 £249,351 2 £11,100 £5,909 £243,442 3 £10,828 £6,180 £237,262 4 £10,545 £6,464 £230,799 5 £10,248 £6,761 £224,038 6 £9,937 £7,071 £216,966 7 £9,612 £7,396 £209,570 8 £9,272 £7,736 £201,834 9 £8,917 £8,091 £193,742 10 £8,545 £8,463 £185,279 11 £8,156 £8,852 £176,427 12 £7,750 £9,259 £167,168 13 £7,324 £9,684 £157,484 14 £6,880 £10,129 £147,356 15 £6,414 £10,594 £136,761 16 £5,928 £11,081 £125,680 17 £5,419 £11,590 £114,090 18 £4,886 £12,122 £101,968 19 £4,329 £12,679 £89,289 20 £3,747 £13,262 £76,027 21 £3,137 £13,871 £62,156 22 £2,500 £14,508 £47,648 23 £1,834 £15,175 £32,473 24 £1,137 £15,872 £16,601 25 £407 £16,601 £0

Generic arithmetic, not financial advice: real offers depend on credit checks, fees, fixes and affordability rules. Product fees and rate changes after a fixed period are not modelled.

All arithmetic runs in your browser. Incomes and property figures are never transmitted.

Guide

How to use it

  1. Enter the property price and your deposit, the difference is what you borrow.
  2. Enter the interest rate. Use the rate itself for a fix you are considering, today’s typical fixes sit in the 4s, your actual offer depends on deposit size and credit.
  3. Set the term. 25 years is traditional, longer terms cut the monthly cost but grow the total interest markedly.
  4. Read the monthly payment and open the year-by-year table, the early years are mostly interest, which is normal and temporary.
  5. Toggle interest-only to see that comparison, and what it leaves unpaid.

Examples

The trade-offs, in numbers

£255K AT 4.5%

A £285,000 home with £30,000 down over 25 years: about £1,417 a month, and roughly £170,000 of interest across the term. The default example in the tool, adjust from there.

25y → 35y

Stretching the same loan to 35 years drops the monthly by around £210 but adds roughly £80,000 of interest. Longer terms are a cash-flow tool with a real price tag.

5% → 10% DEPOSIT

Doubling a small deposit does two things: borrows less, and unlocks cheaper rate brackets (loan-to-value bands at 90%, 85%, 80%). The second effect often matters more than the first.

Method

How it works

The monthly payment uses the standard amortisation formula: the payment that exactly clears the balance, with interest accruing monthly, over the chosen term. The year table applies each payment month by month, splitting it into interest (balance × monthly rate) and repayment (the rest).

Interest-only mode divides the annual interest by twelve and leaves the balance untouched, honest about what that means at term end. Fees, rate changes after a fixed period and insurance are deliberately out of scope, they belong in a broker conversation.

FAQ

Frequently asked questions

How much deposit do I need?

5% is the practical minimum for mainstream lending, 10% opens better rates and 25% the best. Loan-to-value bands are the rate card’s skeleton.

Repayment or interest-only?

Repayment unless you have a genuine repayment vehicle: interest-only leaves the whole loan due at term end, and lenders now demand evidence of the plan. The toggle shows both honestly.

What rate should I type in?

The rate of the product you are actually considering, or a mid-4s placeholder for rough planning. Your offer depends on LTV and credit file, not the advertised best-buy.

Why is so much of my early payment interest?

Interest is charged on the outstanding balance, which is biggest at the start. The table shows the crossover, typically a third of the way in, after which repayment dominates.

Does this include stamp duty and fees?

No, this is the loan itself. The stamp duty calculator handles that cost, and product fees vary by deal.

Is this advice?

No, arithmetic. Affordability, product choice and stress tests are a regulated broker’s or lender’s job.

More tools

Related tools