A £400,000 mortgage is now a realistic borrowing figure for a large number of UK households — not just those buying in London. In Surrey, Berkshire, Hampshire, Buckinghamshire, and the outer Home Counties, a four-bedroom family home regularly commands prices in the £480,000–£550,000 range, making £400k borrowing necessary even with a substantial deposit. In higher-value London boroughs, it often covers just a fraction of the purchase price.
At this loan size, the financial stakes of every decision are meaningfully higher than at £200k or £250k. A 1% difference in interest rate costs roughly £222 per month — £13,320 over a five-year fixed period. The difference between a 25-year and 30-year term is an extra £80,000 in total interest. And allowing a fixed deal to expire onto the SVR even briefly costs £500–£900 per month in avoidable payments. This page gives you the numbers, the context, and the framework to make the right decisions at every stage.
£400,000 Mortgage Calculator
£400k mortgage repayment table — all rates and terms
The table below shows monthly repayments on a £400,000 capital repayment mortgage across seven interest rates and four term lengths. At this loan size, even a 0.5% rate difference moves the monthly payment by roughly £111 on a 25-year term — and the 20-year versus 35-year total interest gap exceeds £187,000.
| Interest rate | 20-year term | 25-year term | 30-year term | 35-year term |
|---|---|---|---|---|
| 3.5% | £2,318 | £2,003 | £1,796 | £1,657 |
| 4.0% | £2,424 | £2,112 | £1,910 | £1,775 |
| 4.5% | £2,531 | £2,222 | £2,027 | £1,895 |
| 5.0% | £2,640 | £2,338 | £2,147 | £2,018 |
| 5.5% | £2,751 | £2,455 | £2,271 | £2,147 |
| 6.0% | £2,866 | £2,577 | £2,398 | £2,277 |
| 6.5% | £2,983 | £2,701 | £2,529 | £2,413 |
Estimates only. Capital repayment mortgage. Fees, insurance and product charges not included.
Term length and total cost — the £400k trade-off
Choosing your mortgage term at £400k has more financial consequence than at lower loan amounts. The four panels below show exactly what each term costs monthly and in total at 4.5% — the difference between the shortest and longest terms is stark both monthly and overall.
The 35-year term saves £636 per month versus the 20-year term — but costs an additional £188,600 in total interest. That monthly saving is real and legitimate if cash flow genuinely demands it, but it comes at the price of nearly half the original loan amount paid in additional interest charges over the full period. If you choose a longer term for affordability, a structured overpayment plan becomes essential. See our overpayment guide for a full breakdown of the savings available at this loan size.
How a £400,000 mortgage payment is calculated
Your lender applies the same amortisation formula used across every UK mortgage product. The formula converts loan amount, interest rate, and term into a single fixed monthly payment that gradually shifts from mostly interest to mostly capital over the course of the term.
M = monthly payment
P = principal (£400,000)
r = monthly rate = annual rate ÷ 12
n = total payments = years × 12
Worked example: £400,000 at 4.5% over 25 years
- r = 4.5% ÷ 12 = 0.375% = 0.00375 per month
- n = 25 × 12 = 300 payments
- M = 400,000 × [0.00375 × (1.00375)³⁰⁰] ÷ [(1.00375)³⁰⁰ − 1]
- M ≈ £2,222 per month
In month one of this mortgage, £1,500 covers interest and only £722 reduces the outstanding balance. The crossover — where more of each monthly payment goes to capital than interest — does not arrive until approximately year 15. This is why overpaying in the first decade on a £400k mortgage produces such disproportionately large savings: every extra pound in those years chips away at a balance still being charged on amounts close to £380,000–£395,000.
On an interest-only basis at the same rate, the monthly payment simplifies to (£400,000 × 4.5%) ÷ 12 = £1,500 per month — a saving of £722 versus repayment. But the full £400,000 remains outstanding throughout, and over 25 years the total interest paid reaches £450,000 — nearly £184,000 more than on a repayment mortgage. At £400k the capital risk of an unplanned interest-only arrangement is very substantial. Read our repayment vs interest-only guide for a full comparison.
Overpayment impact at £400,000
At this loan size the interest saving from overpaying is calculated on the largest base we have covered on this site. Even modest regular overpayments produce savings that comfortably exceed the original loan amount in cumulative interest avoided over the full term.
| Overpay £150/month | Saves approx. £27,500 interest, cuts ~2.5 yrs |
| Overpay £250/month | Saves approx. £45,500 interest, cuts ~4 yrs |
| Overpay £400/month | Saves approx. £68,000 interest, cuts ~6 yrs |
| Overpay £600/month | Saves approx. £95,000 interest, cuts ~8.5 yrs |
Overpaying £250/month on a £400k mortgage saves approximately £45,500 in interest — a guaranteed, risk-free return at your mortgage rate, completely tax-free. For a higher-rate taxpayer this beats the effective after-tax return on most savings accounts. Most lenders allow up to 10% of the outstanding balance per year without an early repayment charge — on £400k that is a penalty-free overpayment allowance of up to £40,000 per year.
Deposit thresholds — LTV tiers for a £400,000 mortgage
At £400k, moving between LTV tiers saves more in absolute monthly terms than at any lower loan size. The table below maps each common LTV threshold against the property price, deposit required, and indicative rate tier.
| Property price | Deposit | LTV | Rate tier | Approx. rate range |
|---|---|---|---|---|
| £421,053 | £21,053 (5%) | 95% | Entry | 5.3–6.8% |
| £444,444 | £44,444 (10%) | 90% | Standard | 4.45–5.5% |
| £470,588 | £70,588 (15%) | 85% | Competitive | 4.15–4.95% |
| £500,000 | £100,000 (20%) | 80% | Best standard | 3.95–4.65% |
| £571,429 | £171,429 (30%) | 70% | Premium | 3.75–4.4% |
Rate ranges are illustrative mid-2025 estimates. Actual rates depend on lender, credit profile, and product type.
The monthly saving from reaching an 85% LTV rather than a 90% LTV deal on £400k is typically £130–£160 per month at current rates. Over a five-year fixed period that saving totals £7,800–£9,600 — a strong financial argument for the additional deposit saving time. Use our deposit planning guide to model how long it will take to reach each threshold.
Real UK buyer scenarios at £400,000
James and Sophie are selling their three-bed in Reading for £390,000. After clearing their £210,000 existing mortgage and transaction costs, they retain approximately £172,000 in equity. They use £100,000 as a 20% deposit on a £500,000 five-bed in Wokingham, keeping £72,000 as a reserve fund. Their new mortgage is £400,000 at 80% LTV.
Their 80% LTV position secures them a five-year fix at 4.1% over 25 years. Monthly repayment: approximately £2,129. Combined gross income is £128,000, so the mortgage represents around 30% of net monthly take-home — well within sustainable limits. They budget £15,000 for stamp duty (as home movers on a £500,000 purchase) and a further £4,000 for solicitor, survey, and moving costs.
Dr. Aisha is a consultant cardiologist earning £105,000. She is purchasing a two-bed flat in South West London for £500,000 with a £100,000 deposit (20%), giving her a £400,000 mortgage at 80% LTV. At standard 4.5× income her maximum is £472,500 — well above the £400k required — but she specifically uses a professional mortgage product to access a rate of 4.05% unavailable to non-professional applicants at this LTV.
Monthly repayment over 20 years: approximately £2,432. Her take-home after tax is approximately £5,800/month. The mortgage represents 41.9% of net income — higher than the typical comfort threshold — but she is single with no dependants and has significant pension contributions reducing her taxable income. She commits to a £300/month overpayment from month one to reduce the balance and the effective term.
Stamp duty on £500,000 as a first-time buyer at the outer edge of FTB relief: approximately £10,000 — 5% on the £200,000 above the £300,000 nil-rate threshold. As a home mover the same property would attract approximately £15,000 in stamp duty — a £5,000 saving that first-time buyer status still affords her at this price point.
Paul and Claire took out a £480,000 mortgage seven years ago. Their balance is now £404,000 with 18 years remaining. Their five-year fix expired last month and their lender's SVR is 7.49%. Their monthly payment has jumped from £2,178 to £3,276 — a monthly increase of £1,098 that is immediately visible in their bank account.
They urgently compare rates using our mortgage calculator and instruct a broker who secures a new five-year fix at 4.45% over the remaining 18 years. New monthly payment: approximately £2,638. Monthly saving versus SVR: £638. Over the five-year fixed period: £38,280 saved.
They also use our stamp duty calculator to confirm there is no additional SDLT on a straight remortgage — there is not, and they are able to proceed without any property transaction costs beyond solicitor fees of approximately £800.
What salary do you need for a £400,000 mortgage?
A £400,000 mortgage sits well above the reach of most single average incomes at standard lending multiples. It is primarily achievable through strong professional salaries, joint applications, or specialist lender products.
| Income scenario | Max at 4× | Max at 4.5× | £400k verdict |
|---|---|---|---|
| £75,000 solo | £300,000 | £337,500 | Below threshold — needs 5× or above |
| £80,000 solo | £320,000 | £360,000 | Specialist lender at 5× needed |
| £89,000 solo | £356,000 | £400,500 | Achievable at 4.5× |
| £100,000 solo | £400,000 | £450,000 | Comfortable at 4× |
| £52,000 + £38,000 joint | £360,000 | £405,000 | Achievable jointly at 4.5× |
| £55,000 + £45,000 joint | £400,000 | £450,000 | Comfortable at 4× |
| £65,000 + £35,000 joint | £400,000 | £450,000 | Comfortable at 4× |
| £80,000 solo (5× professional) | — | — | Achievable at 5× specialist |
Multiples are illustrative. Actual lending depends on outgoings, credit profile, deposit size, and lender policy.
For sole applicants, a £400k mortgage at standard income multiples requires a gross salary of approximately £89,000 at 4.5×, or £100,000 at 4×. These are salaries achievable in senior roles across finance, technology, medicine, law, and engineering — particularly in London and the South East where this borrowing level is most common. Joint applicants find this amount considerably more accessible: combined salaries of £90,000 or more comfortably meet the affordability threshold with most lenders.
Professional mortgage products offering 5× or 5.5× income multiples reduce the solo threshold to £72,500–£80,000. At this level a mortgage broker's knowledge of which lenders offer these products for your specific occupation can make a difference of £40,000–£80,000 in borrowing capacity — purely from choosing the right lender.
When is this calculator most useful?
Common mistakes on a £400,000 mortgage
-
Underestimating stamp duty at this purchase price
Buyers borrowing £400k are typically purchasing in the £440,000–£560,000 range. Stamp duty for home movers on a £500,000 purchase is £15,000. First-time buyers purchasing at exactly £500,000 pay £10,000 — 5% on the £200,000 above the £300,000 nil-rate threshold, right at the outer edge of FTB relief. The gap between these two figures is £5,000 — a number that needs to sit alongside the deposit in your budget from the very beginning of your property search. Use our stamp duty calculator for an exact figure.
-
Not comparing two-year versus five-year fixed rates carefully enough
On a £400k mortgage, the difference between a two-year fix at 4.2% and a five-year fix at 4.55% is about £133/month. Over two years the cheaper deal saves £3,192 — but then you face remortgage costs again, plus exposure to whatever rate environment exists at that point. Over a five-year horizon on £400k, the certainty of a five-year fix often delivers better total value than the slightly lower two-year rate, particularly for borrowers who prefer payment stability.
-
Using a 35-year term without a written overpayment plan
The 35-year term on £400k at 4.5% produces total interest of £396,000 — nearly equal to the original loan. Compared to a 25-year term the extra interest cost is £129,400. If you take the longer term for affordability, commit to a specific monthly overpayment amount in writing and set up the standing order before the mortgage starts. Without this, the good intention to overpay routinely never materialises.
-
Not verifying both credit profiles before a joint application
On a joint application for £400k, the weaker of the two credit profiles determines which lenders will consider the application and the rates available. A single missed payment, an unknown default, or an incorrect entry on one applicant's credit file can shift the rate tier — costing £100+ per month on a loan this size. Both applicants should check all three credit reference agencies at least three months before applying, leaving time to resolve any issues.
-
Failing to account for the ongoing cost of property maintenance at this price point
Properties in the £450,000–£550,000 range — which typically correspond to £400k borrowing — are often larger, older, or in areas with higher associated costs. The general rule of budgeting 1% of property value per year for maintenance means setting aside £4,500–£5,500 annually on top of mortgage payments, insurance, and council tax. This is rarely factored into the initial affordability conversation but materially affects the true monthly cost of ownership.
Frequently asked questions
-
What is the monthly payment on a £400,000 mortgage?At 4.5% over 25 years on a capital repayment basis, monthly payments are approximately £2,222. At 5% the figure rises to £2,338, and at 6% to £2,577. Over a 30-year term at 4.5% the monthly cost drops to £2,027, while over a 20-year term it rises to £2,531. Use the calculator above to model your specific rate and term combination.
-
What salary do I need for a £400,000 mortgage in the UK?At 4.5× income you need at least £88,889 gross per year as a sole applicant. At 4× the threshold rises to £100,000. For joint applicants, combined salaries of £90,000 or more — for example £52,000 and £38,000 — comfortably support a £400k application. Professional mortgage products at 5× income reduce the solo threshold to £80,000 for eligible occupations.
-
How much deposit do I need for a £400,000 mortgage?Borrowing £400,000 on a £444,444 property requires a 10% deposit of £44,444. The minimum 5% deposit on a £421,053 property requires £21,053 and is the floor for most lenders. At this loan size, the monthly saving from reaching 85% LTV (15% deposit on a £470,588 property) is £130–£160/month — making the additional deposit saving particularly worthwhile.
-
How much total interest do you pay on a £400,000 mortgage?At 4.5% over 25 years you pay approximately £266,600 in interest in addition to the £400,000 capital — a total of around £666,600. Over 30 years total interest rises to approximately £329,700, and over 35 years to £396,000. Overpaying £250/month from day one saves approximately £45,500 in interest and cuts around four years off a 25-year term.
-
Is a £400,000 mortgage achievable on a joint income in the UK?Yes, comfortably on a combined income of £90,000 or above at 4.5×. Most lenders combine both salaries before applying the income multiple, making £400k achievable for households earning a combined £88,000–£90,000 with clean credit and manageable outgoings. At a 5× multiple (available with some specialist and professional lenders) a combined income of £80,000 is sufficient.
Related calculators and guides
About the author
✓ Editorially reviewed — all Poqet guides are checked for factual accuracy before publication and updated when UK rates or legislation change. Editorial Policy