UK Mortgage Calculator with Tax & Insurance

The headline mortgage repayment that most UK calculators surface is only part of what a homeowner actually pays each month. The full picture — what brokers and lenders call the true monthly cost — adds Stamp Duty Land Tax (amortised over the holding period or paid upfront), council tax, buildings insurance, and a maintenance reserve on top of principal and interest. This calculator models all four so the figure you compare against your monthly take-home pay is the figure you will genuinely live with, not the headline number lenders use to sell the loan.

What 'true monthly cost' means in UK property

UK mortgage advice has historically focused on the lender's affordability test, which centres on the principal-and-interest (P&I) payment under stress. That test answers a single question — can the borrower service the loan if rates rise — but it doesn't answer the question every household actually cares about, which is: what will I write a cheque for each month once I own this property?

The gap between the two is structural. A typical UK first-time buyer purchasing a £350,000 home with a 10% deposit on a 25-year 4.5% mortgage pays roughly £1,750/month in P&I. That same household will also pay council tax (£120-£300/month depending on band and local authority), buildings insurance (£15-£40/month), and should set aside a maintenance reserve of around 1% of property value per year (£290/month on £350k). Add it up and the true monthly cost is closer to £2,200-£2,400 — 25-40% above the headline P&I figure. That gap is the difference between a borrower who feels comfortable in year three and one who is stretched.

The calculator treats SDLT slightly differently: because Stamp Duty is paid upfront at completion, it's not strictly a monthly cost. But because most buyers add SDLT to their cash-needed-at-completion (alongside deposit, legal fees, and survey), the calculator amortises it over the holding period so you can see the true all-in cost per month of homeownership over the term you intend to hold.

SDLT (Stamp Duty Land Tax) in 2026

Stamp Duty Land Tax applies to property purchases in England and Northern Ireland. Scotland uses Land and Buildings Transaction Tax (LBTT); Wales uses Land Transaction Tax (LTT). The post-1 April 2025 SDLT bands for owner-occupier purchases (not first-time buyer, not additional property) are:

• 0% on the portion up to £125,000
• 2% on the portion £125,001-£250,000
• 5% on the portion £250,001-£925,000
• 10% on the portion £925,001-£1,500,000
• 12% on the portion above £1,500,000

First-time buyer relief in England and Northern Ireland reverted on 1 April 2025 from the temporary £425k/£625k thresholds back to its long-term shape:

• 0% on the portion up to £300,000
• 5% on the portion £300,001-£500,000
• No FTB relief is available on purchases above £500,000 — standard rates apply to the full price

Additional-property purchases (second homes, buy-to-let) carry a 5 percentage point surcharge on every band, applied to the full purchase price. The surcharge was raised from 3% to 5% on 31 October 2024.

The calculator auto-computes SDLT from the property price plus the first-time-buyer and additional-property toggles, so you don't need to look up bands manually. HMRC's Stamp Duty Land Tax guidance on gov.uk is the authoritative source for current rates and corner cases (linked transactions, mixed-use property, multiple-dwellings relief).

Council tax

Council tax is set by your local authority and depends on the property's valuation band, which is determined by the Valuation Office Agency based on the property's market value as at 1 April 1991 in England (1 April 2003 in Wales). There are eight bands A through H, with the band determining a multiplier applied to the local authority's band-D rate.

Typical 2026/27 annual council tax across England by band:

• Band A (lowest): £1,400 average
• Band B: £1,650
• Band C: £1,850
• Band D (the reference band): £2,100
• Band E: £2,550
• Band F: £3,000
• Band G: £3,500
• Band H (highest): £4,200 average

These are averages. Westminster (one of the lowest) charges roughly half the national average at each band; Rutland and parts of the North East charge well above average. The Valuation Office Agency's online lookup at gov.uk gives the band for any address; the local authority website gives the cash amount for the current year.

Most local authorities default to billing across 10 months (April through January) with February and March free, but every authority is required to offer a 12-month payment option on request. The calculator divides annual council tax by 12 to get a monthly equivalent — which is what you should budget against, regardless of how the bill is structured.

Buildings insurance

Buildings insurance is required by virtually every UK lender as a condition of the mortgage offer. Without it, the lender's security against the loan is exposed to the risk of fire, flood, subsidence, and storm damage. Buildings cover is distinct from contents cover — contents is optional and protects what's inside; buildings is compulsory for mortgaged property and protects the physical structure.

Typical 2026 premiums:

• Standard 3-bed semi outside flood risk areas: £150-£250/year
• Larger detached property or higher-value home: £250-£400/year
• Flood-risk postcodes or older listed buildings: £400-£800+/year

A persistent source of confusion is the distinction between reinstatement value and market value. Insurers cover reinstatement — the cost to rebuild the property from scratch on the same plot — which is almost always lower than market value because market value includes the land. A £600,000 London terraced house might have a reinstatement value of £350,000 because the land itself isn't insurable. Under-insuring on reinstatement value is the most common cause of disputed claims; over-insuring on market value is the most common cause of overpaying premiums. The Association of British Insurers publishes a free rebuild cost calculator; the RICS Building Cost Information Service is the trade reference.

The calculator takes annual buildings insurance as a direct input and divides by 12. If you've been quoted a premium in your most recent renewal letter, use that figure rather than a national average for accuracy.

Total monthly cost — two worked examples

Example 1: First-time buyer, £350,000 home, 10% deposit, 25-year mortgage at 4.5%

• Loan: £315,000 at 4.5% over 25 years → P&I ~£1,752/month
• SDLT: £2,500 (FTB relief — 5% on the £50k slice above the £300k threshold; amortised over 25 years adds ~£8/month)
• Council tax: band C, £1,850/year → £154/month
• Buildings insurance: £200/year → £17/month
• Maintenance reserve: 1% of £350k → £292/month
• True monthly cost: ~£2,223

Vs. headline P&I figure of £1,752 — the true cost is 27% higher than what the lender's affordability test centres on. (The £1,752 figure assumes a generic 4.5% rate; for a true-to-product 5-year fixed view with the early-repayment-charge schedule and end-of-fix balance baked in, see our 5-year fixed mortgage calculator.)

Example 2: Mover, £750,000 home, 20% deposit, 25-year mortgage at 4.5%

• Loan: £600,000 at 4.5% over 25 years → P&I ~£3,334/month
• SDLT: £27,500 upfront (2% on £125k-£250k = £2,500, plus 5% on £250k-£750k = £25,000). Amortised over a 10-year holding period that's £229/month
• Council tax: band F, £3,000/year → £250/month
• Buildings insurance: £350/year → £29/month
• Maintenance reserve: 1% of £750k → £625/month
• True monthly cost: ~£4,467 (including SDLT amortised) or £4,238 excluding amortised SDLT

The SDLT alone amortises to £229/month over a 10-year hold — material enough that it should be in the affordability conversation, not treated as a one-off cash hit at completion.

What the calculator does NOT include

Four categories of cost are deliberately excluded so the figure stays comparable across properties:

• Leasehold ground rent and service charges: on flats and some new-build estates, ground rent runs £200-£500/year and service charges £1,000-£5,000/year. These vary so dramatically by property they would distort any cross-comparison. Budget separately if you're buying leasehold.
• Utility bills: gas, electricity, water, broadband, TV licence — roughly £200-£350/month for a typical household — apply equally to renters and owners.
• Mortgage protection / income protection insurance: typically £20-£50/month, optional but advised. Add separately if you intend to take cover.
• Conveyancing, survey, mortgage arrangement fees: one-off completion costs typically £2,000-£4,000 in addition to the deposit and SDLT. Add to your cash-at-completion calculation, not your monthly cost.

The 1% maintenance reserve is the rule of thumb the RICS uses for typical UK housing stock, and the calculator applies it by default. Older properties, listed buildings, and homes with non-standard construction (timber-frame, cob, single-skin brick) routinely run at 2-3% of value per year over a 20-year window. If you're buying anything pre-1900 or with a non-standard construction certificate, override the default upward.

For underlying rules and current rates, HMRC's SDLT guidance on gov.uk, the Valuation Office Agency's council tax band lookup, your local authority's current band-rate publication, and the FCA's Mortgage Conduct of Business handbook are the authoritative references.