UK Mortgage Calculator

Calculate your monthly payments, model overpayments, or compare two mortgages side by side.

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Mortgage amount£200,000

Annual interest rate5%

Mortgage term25 yrs

yrs

Interest only

Monthly overpayment£200

Extra amount on top of your regular payment

One-off lump sum£0

A single overpayment applied at the start. Most lenders cap penalty-free overpayments at 10% of the outstanding balance per year - check your terms.

Overpayment strategy

Keep the same payment, pay off sooner.

Lender limits: Most UK lenders cap penalty-free overpayments at 10% of the outstanding balance per year. Check your mortgage terms before overpaying.

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Monthly payment

£1,112

Total interest

£133,499

Interest saved

£36,280

Interest after overpaying

£97,219

Time saved

6 yrs 1 mo

Interest paid £97,219Saved £36,280

Interest paid Interest saved

Balance & equity over time

Balance Balance with overpayments Equity Equity with overpayments

Year-by-year breakdown

Remaining balance at the end of each year

Year	Balance	Overpaid	Interest (yr)
1	£195,569	£193,119	£8,909
2	£190,935	£185,922	£8,706
3	£186,088	£178,395	£8,493
4	£181,018	£170,522	£8,270
5	£175,716	£162,287	£8,037
6	£170,170	£153,673	£7,794
7	£164,369	£144,664	£7,539
8	£158,301	£135,242	£7,272
9	£151,955	£125,386	£6,994
10	£145,317	£115,077	£6,702
11	£138,374	£104,295	£6,397
12	£131,113	£93,018	£6,078
13	£123,517	£81,222	£5,745
14	£115,573	£68,885	£5,396
15	£107,264	£55,981	£5,031
16	£98,573	£42,484	£4,649
17	£89,483	£28,367	£4,250
18	£79,975	£13,601	£3,832
19	£70,030	Paid off	£3,395
20	£59,629	Paid off	£2,939
21	£48,750	Paid off	£2,461
22	£37,371	Paid off	£1,961
23	£25,469	Paid off	£1,438
24	£13,020	Paid off	£891
25	-	Paid off	£320

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The complete guide

UK Mortgage Calculator: How to Read the Numbers

Use our free UK mortgage calculator to model monthly payments, total interest, and term length. Worked example for a £300k house with a 10% deposit at 4.5%.

A mortgage is the largest contract most people will ever sign, and most of them sign it without checking the total. The headline the lender shows you is the monthly payment. The number that actually matters is the one you only see at the bottom of an amortisation schedule: the total interest you pay over the life of the loan. On a £270,000 mortgage at 4.5% over 25 years, that total is around £180,000. The bank prints the £1,501 monthly because the £180,000 would make you walk out.

Our UK mortgage calculator does the maths the lender does not volunteer. You enter the loan, rate, term, and any overpayments, and it shows the monthly payment, the running balance year by year, and the total interest bill. This guide walks through the formula, a worked example for a £300k house, and the trade-offs the term length hides.

The repayment maths in plain English
How to use the calculator
Worked example: £300k house, 10% deposit, 25 years
Term length trade-offs: 25 vs 30 vs 35 years
Fixed vs tracker vs SVR in 2026

The repayment maths in plain English

The standard UK repayment mortgage runs on one formula:

P = L x r x (1 + r)^n / ((1 + r)^n - 1)

Where P is the monthly payment, L is the loan amount, r is the monthly interest rate (the annual rate divided by 12), and n is the total number of monthly payments (years multiplied by 12).

Try it on a £270,000 loan at 4.5% over 25 years. The monthly rate is 0.045 / 12 = 0.00375. The number of payments is 25 x 12 = 300. Plug it in and you get a monthly payment of about £1,501.

The bit they do not teach you in school is what each payment is actually doing. In month one, the interest charge on the outstanding balance is £270,000 x 0.00375 = £1,012.50. Of your £1,501 payment, only £489 actually pays down the loan. The rest is rent on the money. By year fifteen, the balance has dropped enough that the split flips the other way and capital starts coming off in chunks. This is why a mortgage feels stuck for the first decade and then evaporates in the last five years. The maths is loaded against you at the start by design.

The calculator above runs this formula automatically and shows you the split year by year, so you can see exactly when the curve bends in your favour.

How to use the calculator

Five inputs, two optional. Each one moves the result by a measurable amount.

Step 1: Mortgage amount

The loan, not the house price. If you are buying a £300,000 home with a £30,000 deposit, the mortgage is £270,000. The calculator does not care about the property value. It cares about the borrowed sum.

Step 2: Annual interest rate

Use the rate the lender has quoted you, or a realistic estimate of what you would get today at your LTV band. Mainstream 5-year fixes at 60-85% LTV in mid-2026 have generally been quoted in the low-to-mid 4% range, though actual rates vary by lender, product, and your circumstances - always check current pricing with the lender or an FCA-regulated broker. If you do not know your rate yet, run the calculator at 4.5% and again at 5.5% so you have a floor and a ceiling.

Step 3: Mortgage term

Years. Twenty-five is the historic default. Thirty and thirty-five-year terms have become common for first-time buyers chasing a lower monthly payment. The calculator handles anything from 1 to 40.

Step 4: Monthly overpayment (optional)

Extra cash on top of the standard payment. Most UK fixed deals let you overpay up to 10% of the outstanding balance per year with no penalty. The calculator will then ask whether you want the overpayment to reduce the term (keep paying the same amount, finish sooner) or reduce the payment (recalculate downwards each year, keep the term). Reducing the term saves more interest.

Step 5: One-off lump sum (optional)

A single chunk paid at the start of the mortgage. Useful for modelling what to do with an inheritance, bonus, or matured savings bond.

The results panel shows monthly payment, total interest, interest saved from overpayments, and time saved. The chart underneath plots the running balance year by year, and the table lets you export the full amortisation schedule to CSV.

Worked example: £300k house, 10% deposit, 25 years

Let's run the headline scenario the brief asked for: a £300,000 house, 10% deposit, 4.5% rate, 25-year term.

House price: £300,000
Deposit: £30,000 (10%)
Loan-to-value: 90%
Mortgage amount: £270,000
Rate: 4.5% (illustrative; actual rates at 90% LTV in mid-2026 vary by lender)
Term: 25 years (300 monthly payments)

Drop those numbers into the calculator and the headline outputs are:

Monthly payment: £1,501
Total interest over the life of the mortgage: ~£180,200
Total amount paid back: ~£450,200

That last number is the one most borrowers never see. On a £300,000 house you are handing the bank £450,200 over 25 years, which is £150,200 more than the asking price. The interest bill is roughly 60% of the original loan, all of it earned by the lender doing nothing except waiting.

A few sanity checks. Stamp duty rules change periodically, so confirm the current bands on gov.uk or run the totals on our stamp duty calculator before signing the offer. First-time buyer relief and the standard residential bands move with policy, and the figures shown by the calculator reflect the rates current at the time of use.

The lever that moves this scenario the most is the deposit. Pushing the deposit from £30,000 (10%) to £45,000 (15%) drops the LTV from 90% to 85%, and historically that step has often saved borrowers in the region of a few tenths of a percent on the rate, though the saving varies by lender and market conditions. On the same loan and term that can equate to a meaningful interest saving over 25 years. Model both with our LTV band overpayment calculator before committing, and check current pricing at both LTV bands with the lender.

Term length trade-offs: 25 vs 30 vs 35 years

The most expensive mistake on the calculator is treating the term length as a cosmetic choice. It is not. It is the single biggest determinant of how much the house costs you in total.

Same £270,000 loan at 4.5%, three terms:

25 years: ~£1,501 a month, ~£180,200 total interest
30 years: ~£1,368 a month, ~£222,400 total interest
35 years: ~£1,278 a month, ~£266,800 total interest

Pushing the term from 25 to 35 years cuts the monthly payment by 15%. It also pushes the total interest bill up by roughly 48%. Borrowers chasing affordability take the 35-year mortgage to clear the lender's stress test, and what they have actually bought is an extra ten years of interest charges. £86,600 of extra interest, in this scenario.

The standard counter-argument is that you can overpay later when your income rises, effectively shortening the term yourself. The maths supports this if you actually do it. Most people do not. Our should I overpay my mortgage walkthrough digs into how the discipline tends to fail in practice, and how to build a system that makes overpayments automatic rather than aspirational.

The honest take: take the longest term you can stomach to give yourself a buffer, then act as if you took the shortest. Set the standing order at the 25-year level even if you signed a 35-year contract. The flexibility is real, the cost only kicks in if you use it.

Fixed vs tracker vs SVR in 2026

The Bank of England base rate has been in the mid-4% range through mid-2026, which is the cheapest borrowing has been since the post-2022 spike. Always check the current base rate on the Bank of England website. The three product types each price off that rate differently.

A fixed-rate deal locks your rate for 2, 3, 5, or occasionally 10 years. Mainstream 5-year fixes at 60-75% LTV in mid-2026 have generally been quoted in the low-to-mid 4% range, with 2-year fixes often a small margin cheaper because the lender is taking less duration risk - actual rates vary by lender and product. A fix buys budget certainty and protects you if rates rise. It costs you optionality if rates fall, because the early-repayment charge will eat any savings from breaking the deal early.

A tracker moves with the base rate plus a margin (commonly base plus a percentage point or so, depending on the lender and LTV). If the BoE cuts, your payment usually falls the following month. If the BoE hikes, it rises. Trackers often allow overpayments with no early-repayment charge, which is the underrated feature - check the specific product terms. They suit borrowers who can absorb a rate shock and want the flexibility to remortgage or repay whenever.

The Standard Variable Rate (SVR) is what you fall onto when your deal ends, and it is almost always the worst rate the lender offers. SVRs in 2026 have generally been running noticeably above mainstream fix pricing, which on a £270,000 mortgage can add several hundred pounds to the monthly payment versus a fresh fix. Drifting onto the SVR for even a few months can cost more than the cost of arranging a remortgage.

Which product fits depends on your view of rates and your tolerance for payment changes. If you think the BoE cuts further over the next year or two, a 2-year fix or a tracker gives you the chance to benefit. If you think rates are sticky, a 5-year fix locks in today's pricing before any inflation flare-up pushes them back up. The general rule, regardless: start shopping for your next deal around six months before the current one ends. Most lenders let you secure a rate up to six months in advance, so you have a fallback option in your back pocket. Use our remortgage breakeven calculator to work out when a switch pays for itself once fees are included, and read UK mortgage types in 2026 for the full landscape. This is general information, not personal advice - speak to an FCA-regulated mortgage broker for a product recommendation.

If you have spare cash and are not sure whether to overpay or invest it, our invest vs pay off mortgage calculator models both sides on identical assumptions. The general framing is that a 4.5% mortgage rate is effectively a guaranteed 4.5% tax-free return, which compares favourably to cash savings rates but historically loses to long-run equities. Whether you take the certain return or the higher-expected return depends on your circumstances - past performance does not guarantee future results, and the value of investments can fall as well as rise.

Frequently asked questions

How is the monthly payment on a UK repayment mortgage calculated?

The standard formula is P = L * r * (1+r)^n / ((1+r)^n - 1), where L is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the number of monthly payments. On a £250,000 mortgage at 4.5% over 25 years that works out to about £1,390 a month. The calculator above runs this exact formula and then layers overpayments on top.

What is the trade-off between a 2-year and 5-year fix?

A 2-year fix gives you the option to remortgage sooner, which tends to suit borrowers who expect rates to fall. A 5-year fix gives more budget certainty over a longer window. Many owner-occupiers have historically defaulted to 5-year fixes in volatile rate environments. The hidden cost of a 2-year fix is the remortgage admin (and any new arrangement fee) every two years. This is general information, not advice for your circumstances - speak to an FCA-regulated mortgage broker for a recommendation.

How much can I borrow on my income?

Most UK lenders typically cap at around 4.5x your annual gross income (combined for joint applications), with some lenders stretching to around 5.5x for higher earners or specific professional schemes. That is the headline figure. On top of it, lenders run an internal affordability assessment that factors in your outgoings, credit commitments, and dependants, which often pulls the real maximum below the headline multiple. Actual lending criteria vary by lender and change over time.

What is loan-to-value (LTV) and why does it matter so much?

LTV is the ratio of your loan to the property's value. Lenders price in bands at 60%, 75%, 85%, 90%, and 95%. Each step down to a lower band buys you a cheaper rate because the lender's risk drops. Moving from 90% to 85% LTV on a £400,000 home costs around £20,000 of extra deposit but can save 0.3-0.5 percentage points on the rate, which usually pays for itself inside a 5-year fix.

How much can I overpay without a penalty?

Almost every UK fixed-rate mortgage allows you to overpay 10% of the outstanding balance per year with no early-repayment charge. On a £250,000 mortgage that is £25,000 a year of headroom. Check your specific mortgage offer, because a small number of products use lower limits. Tracker and SVR mortgages usually allow unlimited overpayments.

Is overpaying my mortgage better than investing the money?

It depends on the rate and your circumstances. Overpayments effectively earn a guaranteed, tax-free return equal to your mortgage rate. A 4.5% mortgage rate is therefore broadly comparable to a 4.5% risk-free savings rate. Long-run global equities have historically returned around 5-7% real, but past performance does not guarantee future results, and the value of investments can fall as well as rise. Investing inside a Stocks and Shares ISA may win on expected value but loses on certainty. This is general information, not personal advice - the right answer depends on your tax position, time horizon, and risk tolerance.

What happens when my fixed-rate deal ends?

You roll onto the lender's Standard Variable Rate (SVR), which is almost always the worst rate they offer. The fix to use is to start shopping for a remortgage about six months before your current deal ends. You can usually lock a new rate up to six months in advance, so you have a fallback if rates rise in the meantime. Drifting onto the SVR for even a few months costs hundreds of pounds.

Do I need a mortgage broker?

A broker often has access to lenders you cannot approach directly and may know which lenders are more flexible on specific situations (self-employed income, recent credit issues, large deposits from family). Fee-free brokers are typically paid by the lender. Fee-charging brokers (often in the £300-£500 range) can sometimes pay for themselves on the difference in rate. Mortgage advice in the UK is regulated by the FCA - always verify the broker is on the FCA register before signing anything.

How much mortgage can I get on a £40,000 salary?

Most UK lenders typically cap at around 4.5x annual income, which on a £40,000 salary means roughly £180,000. Some lenders stretch to around 5.5x for higher earners or specific professional schemes, which could take it closer to £220,000. Your actual offer depends on outgoings, credit commitments, dependants, and existing debt - and lending criteria vary by lender and change over time. Use the house affordability calculator to model the realistic ceiling rather than the headline multiple, because the internal affordability assessment usually trims the maximum below 4.5x once outgoings are factored in.

Is a 30-year mortgage worth it?

It depends what you do with the cash you free up. On a £270,000 loan at 4.5%, the 30-year cuts your monthly payment by around £133 versus a 25-year, at a cost of roughly £42,000 in extra total interest. If the £133 a month goes into a Stocks and Shares ISA earning 7%, you would have around £160,000 after 30 years, which more than covers the extra interest. If it disappears into lifestyle spending, you have paid the bank £42,000 for nothing. The 30-year is worth it only if you actually invest the difference, which most borrowers do not.