25 vs 35-Year Mortgage: What Extending the Term Costs You in 2026
Stretching a 25-year mortgage out to 35 years cuts the monthly payment by roughly 15%. On a £200,000 loan at the Bank of England's April 2026 quoted 75% LTV five-year fixed rate of 4.32%, that means £924/month instead of £1,091/month — a saving of £167/month. The trade-off is paid back in interest. The same £200,000 loan accrues £127,399 in interest over 25 years, but £188,224 over 35 years — an extra £60,825 for the lender, in exchange for the lower monthly bill.
This piece lays out the maths at every typical loan size from £100,000 to £400,000, shows what happens to your equity-build curve when you extend, and explains the rules lenders apply to maximum term lengths. It does not tell you whether to extend; that depends on your wider finances. Speak to a qualified mortgage adviser before acting.
The headline numbers (BoE quoted rate, April 2026)
The Bank of England publishes a monthly file of quoted interest rates on advertised mortgage products. The most cited series for owner-occupier mainstream lending is 75LTV5Y — the advertised rate on a 75% loan-to-value, five-year fixed mortgage. As of the April 2026 release it stood at 4.32%, down from 4.62% a year earlier (Bank of England, Quoted Household Interest Rates, data accessed 24 May 2026).
Applying that rate to a standard repayment mortgage at common loan sizes gives the following monthly payments and lifetime interest figures:
| Loan | 25-year monthly | 30-year monthly | 35-year monthly | 25→35 monthly saving | 25→35 extra interest |
|---|---|---|---|---|---|
| £100,000 | £546 | £496 | £462 | £83 (15%) | £30,412 |
| £150,000 | £818 | £744 | £693 | £125 (15%) | £45,619 |
| £200,000 | £1,091 | £992 | £924 | £167 (15%) | £60,825 |
| £250,000 | £1,364 | £1,240 | £1,155 | £209 (15%) | £76,031 |
| £300,000 | £1,637 | £1,488 | £1,387 | £250 (15%) | £91,237 |
| £350,000 | £1,910 | £1,736 | £1,618 | £292 (15%) | £106,443 |
| £400,000 | £2,183 | £1,984 | £1,849 | £334 (15%) | £121,650 |
Two patterns are stable across every loan size. First, the monthly saving from 25→35 is almost exactly 15% at this interest rate — the percentage is set by the rate, not the loan amount. Second, the extra lifetime interest scales linearly with the loan — roughly £304 per £1,000 borrowed, again because the term and rate fix the ratio.
You can see how the monthly figure for any specific loan compares to your local council tax and energy costs using the Homecost true-cost tool — type any UK postcode to see the full monthly outgoing on a property on that street.
The interest stack at a glance
Lifetime interest paid to the lender, in pounds, at the BoE-quoted 4.32%:
| Loan | 25-year interest | 30-year interest | 35-year interest |
|---|---|---|---|
| £100,000 | £63,700 | £78,577 | £94,112 |
| £150,000 | £95,549 | £117,865 | £141,168 |
| £200,000 | £127,399 | £157,154 | £188,224 |
| £250,000 | £159,249 | £196,442 | £235,280 |
| £300,000 | £191,099 | £235,730 | £282,336 |
| £350,000 | £222,948 | £275,019 | £329,392 |
| £400,000 | £254,798 | £314,307 | £376,448 |
For a £300,000 loan, the gap between the shortest and longest mainstream term is £91,237 — roughly a year of UK median household income, paid in interest, for the privilege of a £250/month lower mortgage payment. The 30-year option splits the difference: £149 cheaper than 25 years per month, £44,631 more in interest. Our companion piece on the monthly cost of a £300,000 mortgage walks through the same loan size from the affordability side.
What the term does to your equity curve
Reducing the monthly payment by stretching the term doesn't just shift interest to the lender; it slows down how fast you own the house. The capital portion of each payment is much smaller in the early years on a longer term. Below is the equity built by the end of year 5 on each typical loan size, at 4.32%:
| Loan | Equity built by year 5 — 25-year term | Equity built by year 5 — 30-year term | Equity built by year 5 — 35-year term |
|---|---|---|---|
| £150,000 | £18,615 | £13,640 | £10,244 |
| £200,000 | £24,819 | £18,186 | £13,658 |
| £250,000 | £31,024 | £22,733 | £17,073 |
| £300,000 | £37,229 | £27,280 | £20,487 |
On a £200,000 loan, the 35-year borrower has built about £11,000 less equity by the end of a typical five-year fix than the 25-year borrower. That matters at remortgage: a slower equity build means staying in a higher loan-to-value band for longer, which usually means a higher quoted rate at the next fix. Our piece on the equity-build curve relative to rent paid breaks down this mechanic in more detail.
The figures above assume a flat property value. A rising house price boosts equity by the same amount on any term; a falling one cuts it. The relative gap between terms is what's load-bearing here, not the absolute headline.
The rules: what determines the maximum term
UK mortgage term length is governed at three different levels.
- FCA Mortgages Conduct of Business (MCOB) affordability rules. Under MCOB 11.6, a regulated lender must satisfy itself that the borrower can afford the mortgage throughout its life, including allowing for plausible interest rate changes. The longer the term, the longer the lender's affordability obligation runs.
- Retirement-age cap. Most lenders set a maximum age at the end of the mortgage term — commonly 70, 75 or 80 — to satisfy the MCOB requirement that affordability continues into retirement. A 35-year-old borrower can usually get a 35-year mortgage; a 50-year-old borrower typically cannot. Each lender publishes its own age cap; the cap is not set by regulation.
- Lender appetite at the long end. The standard maximum advertised term across most high-street lenders is 40 years; a handful of specialist lenders go further with full-life products (covered in a separate piece). Not every borrower will qualify for the maximum, even within the published policy.
None of these rules require the borrower to choose a specific term. A borrower offered a 35-year mortgage is generally free to take a shorter one if the monthly affordability passes.
Overpayments: the underwritten escape hatch
Most fixed-rate mortgages permit overpayments of up to 10% of the outstanding balance per calendar year without an early repayment charge. That figure is set by the individual lender and product, not by regulation — check your offer letter for the exact wording. Overpayments knock years off the term and the corresponding interest bill, regardless of the headline term the mortgage was written on.
For illustration only: a £200/month overpayment on the £200,000 / 35-year / 4.32% mortgage shortens the effective term to roughly 26 years and saves roughly £40,000 in lifetime interest, while still leaving the underlying contractual payment at the lower 35-year figure if you ever need to fall back to it. The exact figure depends on when in the year the overpayment falls and how the lender credits it; gov.uk's page on repaying a mortgage early sets out the headline mechanics.
The optionality is one of the reasons some borrowers take a longer headline term and overpay when they can — it floors the payment in lean months while still allowing accelerated capital pay-down in better ones. Whether that suits your specific position is a question for a qualified adviser.
What is — and isn't — in these figures
A few things the table does not factor in.
- Future rate resets. The figures assume the 4.32% quoted rate runs for the full term. In reality a 5-year fix resets every five years to the then-prevailing rate. The Bank of England's 75LTV5Y series has swung between roughly 1.5% and 6.1% since 2018 (Bank of England quoted rates file), so the lifetime interest figure is a useful comparison metric across terms but not a forecast.
- Inflation. A flat nominal monthly payment over 35 years is worth materially less in real terms in year 30 than in year 1. That is one structural reason longer terms appeal at higher rates, even with the lifetime interest penalty.
- Product fees. Most fixed-rate products carry an arrangement fee in the £0-£1,999 range. Add that to the front-end cost before comparing two products.
- Insurance, council tax, energy, and maintenance. All ignored here — see the Homecost true-cost tool for those running costs at a specific address, or our cost-intelligence guides for the standard line items by purchase price.
Bottom line — and the standard caveat
A longer term is, in straight cash terms, more expensive over the life of the mortgage. It is not, on its own, financially worse: a lower monthly payment can leave room for pension contributions, an ISA, an emergency fund, or simply the headroom to absorb a rate reset without remortgaging in distress. Pure interest minimisation argues for the shortest term you can afford; pure cash-flow flexibility argues for the longest. The right answer depends on the rest of your financial picture, your age, your employment outlook, and what else competes for the marginal pound.
This piece is general information, not financial advice. Speak to a qualified mortgage adviser or independent financial adviser before choosing a term length, and double-check your specific product's overpayment allowance and early repayment charges before relying on them.
Calculations: standard amortisation formula at 4.32% (Bank of England 75LTV5Y, April 2026 file, accessed 24 May 2026), repayment-only mortgage, full-term horizon, flat rate, no fees. Term-extension delta cross-checked at each £50k loan rung from £100k to £400k.