How it works
How UK mortgages work
This mortgage UK calculator gives you the real monthly payment on a repayment home loan in England, Scotland, Wales or Northern Ireland — the same number a broker quotes after the product fees and stress tests settle. Plug in loan, rate and term, and the answer lands before a kettle boils.
In the UK, almost all new mortgages are repayment (capital & interest) — you pay down the loan over the agreed term, usually 25 years, and own the property outright at the end. Interest-only mortgages still exist but are now niche (mostly buy-to-let). The rate is usually fixed for an initial deal period (2, 5 or 10 years) and then reverts to the lender's Standard Variable Rate (SVR).
Lenders look at Loan-to-Value (LTV) — the loan as a percentage of the property value — and your affordability (income, existing debt, commitments). The lower your LTV, the better the rate. 60% LTV or lower usually unlocks the best deals. Before signing, most buyers pair this calc with the stamp duty calculator and the compound interest calculator to see the full picture — deposit, tax and long-run cost.
The monthly payment formula, plainly
The standard amortisation formula does two things simultaneously: it charges monthly interest on the outstanding balance, and it chips away at the capital so the balance hits zero at the end of the term.
Worked example: £250,000 at 4.5% over 25 years
Monthly rate r = 0.045 / 12 = 0.00375. Term n = 25 × 12 = 300 months.
Payment = 250,000 × (0.00375 × 1.00375^300) / (1.00375^300 − 1) ≈ £1,389.58.
Total paid over 25 years ≈ £416,874. Interest paid ≈ £166,874.
In month 1, roughly £937.50 is interest and £452.08 is capital. By the final year, almost every pound goes on capital.
What changes your monthly payment
Small tweaks have big long-run effects. Here is what moves the number most:
| Change | Impact on £250k / 4.5% / 25y baseline |
|---|---|
| +1% rate (to 5.5%) | +£145/month, +£43,500 over term |
| −1% rate (to 3.5%) | −£138/month, −£41,400 over term |
| Term 30 instead of 25 | −£123/month, +£48,400 total interest |
| Term 20 instead of 25 | +£192/month, −£47,400 total interest |
| Overpay £100/month | Mortgage-free ~2.5 years early, save ~£21k interest |
Fixed, tracker or variable?
Most borrowers pick a fixed deal (2, 5 or 10 years) for certainty. A tracker follows the Bank of England base rate plus a margin — cheaper when base rates fall, painful when they rise. The Standard Variable Rate is the lender's default after your deal ends and is nearly always the most expensive option; remortgaging a month or two before deal-end usually saves money.
Overpayments: the quiet superpower
Most fixed-rate mortgages allow you to overpay up to 10% of the balance per year without an Early Repayment Charge (ERC). Even small overpayments save outsized interest because they reduce the balance compound-daily.
An extra £100/month on a £250,000 mortgage typically shaves 2–3 years off the term and saves £15,000–£25,000 depending on the rate. Check your own lender's overpayment policy and any ERC before you commit.
Other costs to budget for
- Stamp Duty Land Tax — see our stamp duty calculadora. First-time buyers get relief up to £425,000.
- Arrangement / product fees — typically £0–£1,999. Can be added to the loan but you'll pay interest on them.
- Valuation, survey, conveyancing and searches — budget £1,500–£3,000 for the legal and survey stack.
- Buildings insurance — lenders require it from completion day. Compare annually to keep premiums honest.
Affordability — how lenders really decide
Behind the income-multiple rule of thumb sits a much more granular affordability assessment. Lenders stress-test your ability to pay in three ways: at the product rate, at the lender's SVR and at an FCA-mandated stress scenario (typically SVR + 1 %). They then subtract committed outgoings from net income to see whether the mortgage still fits.
- Gross-to-net income: salary, bonuses (usually 50 % counted), guaranteed overtime, rental income minus costs, pension drawdown.
- Committed outgoings: credit-card minimum payments, personal loans, car finance (including PCP balloon), child-care costs, alimony, school fees.
- Lifestyle assumptions: ONS-style cost-of-living buffer per adult and per child, adjusted for postcode.
- Credit history: missed payments, defaults, CCJs, IVAs, payday loans in the last 12 months, and hard-search density all move affordability caps.
Amortisation demystified — a worked 12-month table
The payment stays flat at £1,389.58 in the baseline example, but the split between interest and capital shifts every single month. Here is the first year of the schedule, rounded to the nearest pound.
| Month | Payment | Interest | Capital | Balance |
|---|---|---|---|---|
| 1 | £1,390 | £938 | £452 | £249,548 |
| 2 | £1,390 | £936 | £454 | £249,094 |
| 3 | £1,390 | £934 | £456 | £248,638 |
| 6 | £1,390 | £928 | £462 | £247,263 |
| 12 | £1,390 | £917 | £473 | £244,396 |
| 60 | £1,390 | £819 | £571 | £217,935 |
| 120 | £1,390 | £649 | £741 | £172,427 |
| 180 | £1,390 | £428 | £962 | £113,231 |
| 240 | £1,390 | £142 | £1,248 | £36,478 |
| 300 | £1,390 | £5 | £1,385 | £0 |
Four concrete borrower scenarios
Real numbers on three real-ish buyers and one landlord. All use 2025/26 market rates at 60–85 % LTV; swap in your own figures where the narrative fits.
Scenario A — first-time buyer in Manchester
Emily, 28, earns £42,000 gross. She has saved £22,000 for a £220,000 terrace, borrowing £198,000 at 90 % LTV. Best 5-year fix at 90 % LTV is 4.65 %. Monthly payment on a 30-year term = £1,020. Stamp Duty is £0 thanks to first-time buyer relief. Total cost over the five-year fix ≈ £61,200, of which £44,200 is interest. Her lender's affordability cap at 4.5 × income was £189,000 — the gap was closed by showing £5k of parental gift and a cleaner credit file.
Scenario B — remortgaging in Bristol
Amy and Josh owe £168,000 with 18 years left. They currently pay £1,260 at 5.40 % after their deal expired into SVR. A new 5-year fix at 4.15 % (70 % LTV) cuts their payment to £1,125, saving £135 a month or £8,100 over the fix. Product fee is £999, which they add to the loan — real saving after fee is about £7,100.
Scenario C — mover upgrading in Edinburgh
The Grants sell at £380,000 and buy at £525,000, porting £220,000 of their existing 3.79 % deal and borrowing an extra £155,000 at today's 4.35 % (the lender splits the sub-accounts). LBTT on the £525k buy is about £27,350. Total monthly payment across both sub-accounts rises from £1,140 to £2,050. They stretch the term back out to 22 years to keep it within affordability.
Scenario D — buy-to-let in Nottingham
Arun buys a £180,000 flat to let. 25 % deposit (£45,000) and a £135,000 interest-only buy-to-let mortgage at 5.25 %. Interest-only payment = 135,000 × 0.0525 / 12 ≈ £590/month. Gross rent at £1,100/month gives stress-tested cover of (1,100 × 12) / (135,000 × 0.0625) = 1.56x — above the 125 % minimum for limited companies. Stamp Duty 5 % surcharge lands at £8,250.
Mortgage pitfalls to sidestep
Most regrets trace back to half a dozen avoidable decisions. Here they are in plain English.
- Taking the longest possible term by default. A 40-year term looks affordable, but a 25-year term on the same rate saves you roughly £60k of interest on a £250k loan. If you can pay a bit more monthly, pay a lot less over time.
- Adding every fee to the loan. A £999 product fee added to a 30-year mortgage at 4.5 % costs an extra £820 in interest over the term. Pay it from savings if you can.
- Falling onto SVR. SVR is currently around 7 % at most UK lenders. Missing your remortgage window for even three months on a £200k balance costs about £1,200.
- Over-committing on protection you don't need. Credit-life and income-protection add-ons sold with mortgages are often overpriced; buy them from a specialist broker or MoneyHelper resources instead.
- Under-insuring the property. The rebuild cost (not market value) is what your policy needs to match. Most insurers give a sum insured calculator — use it.
Types of UK mortgage — beyond fixed versus tracker
Most headlines talk about 2-year fixes and base-rate trackers, but the lender shelf is wider than that. Knowing the options makes it easier to pick the product that actually fits your life, not just the first figure a comparison site shows.
- Offset mortgage — links the loan to a savings account. You pay interest on the loan balance minus the savings balance. Useful for self-employed borrowers with lumpy cash flow, and for people who still want instant access to savings while shortening the mortgage.
- Discount mortgage — variable rate set a fixed margin below the lender's SVR. Cheaper headline rate, but the lender can move the SVR at any time.
- Cashback mortgage — lender pays £300–£1,000 on completion. Often bundled with a slightly higher rate, so do the total-cost maths.
- Green mortgage — preferential rate or cashback for buying a property with EPC A or B. The discount is typically 0.05–0.15 percentage points — modest but real if you already meet the criteria.
- Flexible mortgage — explicit overpayment, underpayment and payment-holiday features. Useful for contractors and anyone with variable income.
- Shared-ownership mortgage — designed to sit alongside a housing association share; lenders model the rent alongside the repayment in affordability.
- Joint borrower sole proprietor — a family member boosts affordability without going on the title deeds. Common way parents help adult children while avoiding Stamp Duty surcharges.