Mortgage Calculator UK 2026: Complete Guide to Monthly Repayments, Stamp Duty & Affordability

Introduction

Buying a home is the single biggest financial commitment most people will ever make. Yet when you start looking at mortgage rates, deposit sizes, and stamp duty thresholds, it is easy to feel overwhelmed by the sheer number of variables. A seemingly small difference in interest rates — say, 4.5% versus 5% — can cost you tens of thousands of pounds over a 25-year term. And that is before you even think about stamp duty, lender arrangement fees, and valuation costs.

That is why we built the Mortgage Calculator UK. This tool gives you an instant, accurate picture of your true mortgage costs — including monthly repayments, total interest over the term, stamp duty, and loan-to-value (LTV) ratio. It handles first-time buyer relief, different mortgage terms from 15 to 40 years, and gives you a clear breakdown of every cost involved.

This guide walks you through exactly how to use the calculator, explains every formula behind the numbers, and gives you real-world examples for the 2025–26 property market.

How to Use This Calculator

The Mortgage Calculator UK is designed to be fast and comprehensive. Here is exactly how to use it:

1. Enter the Property Price — Input the purchase price of the property you are considering. For a realistic estimate, look at properties in your target area on Rightmove or Zoopla.
2. Enter Your Deposit Amount — This is the cash you have saved for the purchase. A 10–20% deposit is typical, though first-time buyers can sometimes buy with as little as 5%.
3. Enter the Interest Rate — Use the rate you have been quoted by a lender, or a current average rate (around 4.5% for a 2-year fix in 2025–26) as a benchmark.
4. Choose Your Mortgage Term — 25 years is the standard, but longer terms (30–40 years) mean lower monthly payments at the cost of more total interest.
5. Check First-Time Buyer Status — If you are a first-time buyer, tick the box to see your stamp duty relief, which can save you thousands.
6. Read Your Results — The calculator instantly shows your monthly payment, total repayment, total interest, stamp duty, LTV ratio, and deposit percentage.

For a full picture of your home-buying budget, pair this calculator with our Income Tax Calculator UK to understand your take-home pay and what you can realistically afford in monthly payments.

Complete Formula Breakdown (With 2025–26 UK Examples)

Understanding the maths behind your mortgage helps you compare deals, negotiate with lenders, and plan your finances with confidence. Here is every formula the calculator uses, explained step by step with real UK examples.

Step 1: Calculate the Loan Amount

Loan Amount = Property Price − Deposit

Example: You are buying a £300,000 property with a £60,000 deposit (20%).
Loan Amount = £300,000 − £60,000 = £240,000

Step 2: Calculate the Loan-to-Value (LTV) Ratio

LTV = (Loan Amount ÷ Property Price) × 100

Example: £240,000 ÷ £300,000 × 100 = 80% LTV

LTV is one of the most important factors lenders use to set your interest rate. A lower LTV means you are borrowing less relative to the property value, which reduces the lender's risk. Typically:

• 60% LTV (40% deposit): Best available rates
• 75% LTV (25% deposit): Very good rates
• 80% LTV (20% deposit): Standard competitive rates
• 90% LTV (10% deposit): Higher rates, may need MIG
• 95% LTV (5% deposit): Highest rates, limited options

Step 3: Calculate Monthly Mortgage Payments

Monthly payments are calculated using the standard amortisation formula:

M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]

Where:

• M = Monthly payment
• P = Loan amount (£240,000)
• r = Monthly interest rate (annual rate ÷ 12, e.g., 4.5% ÷ 12 = 0.00375)
• n = Number of monthly payments (term × 12, e.g., 25 × 12 = 300)

Example: £240,000 loan at 4.5% over 25 years:

• Monthly rate: 4.5% ÷ 12 = 0.00375
• Number of payments: 25 × 12 = 300
• Monthly payment: £1,334

Step 4: Calculate Total Repayment and Total Interest

Total Repayment = Monthly Payment × Number of Payments
Total Interest = Total Repayment − Loan Amount

Example:

• Total Repayment: £1,334 × 300 = £400,267
• Total Interest: £400,267 − £240,000 = £160,267

This means over 25 years, you will pay £160,267 in interest alone — more than 66% of your original loan amount. This is why getting the best possible interest rate and considering a shorter term can save you tens of thousands of pounds.

Step 5: Calculate Stamp Duty (SDLT)

Stamp Duty Land Tax in England and Northern Ireland uses a progressive band system. For a non-first-time buyer:

• 0% on the first £250,000
• 5% on £250,001 – £925,000
• 10% on £925,001 – £1,500,000
• 12% on amounts above £1,500,000

Example (non-first-time buyer, £300,000 property):

• 0% on £250,000 = £0
• 5% on £50,000 (£300,000 − £250,000) = £2,500
• Total Stamp Duty: £2,500

First-time buyer relief: If you are a first-time buyer purchasing a property up to £625,000:

• 0% on the first £425,000
• 5% on the portion between £425,000 and £625,000

For a £300,000 property, a first-time buyer pays £0 stamp duty — saving £2,500 compared to a non-first-time buyer.

Real-Life Examples: Three UK Mortgage Scenarios for 2025–26

Scenario 1: First-Time Buyer — Manchester, £250,000 Flat

Tom and Sarah are first-time buyers purchasing a two-bedroom flat in Manchester for£250,000. They have saved a 10% deposit (£25,000) and secured a 4.5% interest rate on a 30-year term.

• Loan Amount: £250,000 − £25,000 = £225,000
• LTV: 90%
• Monthly Payment: £1,140
• Total Repayment: £1,140 × 360 = £410,400
• Total Interest: £410,400 − £225,000 = £185,400
• Stamp Duty: £0 (first-time buyer relief up to £425,000)

With their combined income of £55,000, their monthly payment of £1,140 is affordable at roughly 25% of their take-home pay. By choosing a 30-year term over 25 years, they save £135 per month on their payment but will pay an extra £34,000 in interest over the life of the mortgage.

Scenario 2: Moving Up — Birmingham, £400,000 House

James and Emma are selling their first home and moving to a larger family home in Birmingham for £400,000. They have £100,000 equity from their sale (25% deposit) and have locked in a 4.2% 5-year fixed rate on a25-year term.

• Loan Amount: £400,000 − £100,000 = £300,000
• LTV: 75%
• Monthly Payment: £1,617
• Total Repayment: £1,617 × 300 = £485,100
• Total Interest: £485,100 − £300,000 = £185,100
• Stamp Duty: 0% on £250k + 5% on £150k = £7,500

Their 75% LTV qualifies them for the best available rates. The 5-year fix gives them payment certainty while their children are young. The £7,500 stamp duty is a significant upfront cost they have budgeted for as part of the moving process.

Scenario 3: Buy-to-Let Investor — Leeds, £180,000 Property

Priya is a buy-to-let investor purchasing a one-bedroom flat in Leeds for£180,000 with a 25% deposit (£45,000) at a5% interest rate on a 25-year term.

• Loan Amount: £180,000 − £45,000 = £135,000
• LTV: 75%
• Monthly Payment: £789
• Total Repayment: £789 × 300 = £236,700
• Total Interest: £236,700 − £135,000 = £101,700
• Stamp Duty: 0% on £250k = £0 (under £250k threshold, plus 3% surcharge for BTL)

Note: Buy-to-let properties incur a 3% SDLT surcharge on top of standard rates. For a £180,000 purchase, the total stamp duty is 3% of £180,000 = £5,400. Priya expects £850/month in rent, giving her a positive cash flow of £61/month before maintenance costs and letting agent fees.

Key Things to Know About UK Mortgages in 2025–26

• Interest rates are stabilising: After the sharp rises of 2022–23, mortgage rates have settled at 4–5% for 2025–26. The Bank of England base rate is expected to remain steady through mid-2026.
• Affordability tests are strict: Most lenders cap borrowing at 4.5× your annual income. Some go up to 5.5× for high earners or certain professions like doctors and accountants.
• 5-year fixes are popular: With rates stabilising, many buyers are choosing 5-year fixes for payment certainty. The rate difference between 2-year and 5-year fixes has narrowed to just 0.3%.
• First-time buyer schemes: The 95% mortgage guarantee scheme and Help to Buy equity loan (in some regions) are still available, making it possible to buy with a 5% deposit.
• Stamp duty thresholds: The £250,000 0% band and first-time buyer relief up to £425,000 are now permanent features of the SDLT system.

Tips to Get the Best Mortgage Deal in 2025–26

1. Improve your credit score before applying. Check your credit report on Experian, Equifax, and TransUnion. Pay off credit card balances, correct any errors, and register on the electoral roll. A 50-point improvement can make a 0.5% difference in your offered rate.
2. Save for at least a 10% deposit. A 10% deposit (90% LTV) vs a 5% deposit (95% LTV) typically means a 0.75–1% lower interest rate. On a £225,000 loan, that saves you £1,700–£2,250 per year in interest.
3. Consider a longer term to start, then overpay. A 35-year term gives you lower mandatory monthly payments, but most lenders allow overpayments of up to 10% per year without penalty. This flexibility lets you pay off your mortgage faster when you can afford it.
4. Get an Agreement in Principle (AIP) early.An AIP from a lender shows sellers and estate agents you are serious and financially qualified. It is free and doesn't affect your credit score if done through a soft search.
5. Use a mortgage broker. A whole-of-market broker can access deals not available directly to consumers. Their fee (typically £300–£500 or a percentage of the loan) is often offset by the better rate they secure.
6. Factor in all upfront costs. Beyond the deposit and stamp duty, budget for valuation fees (£200–£1,500), solicitor fees (£800–£2,000), survey costs (£500–£1,500), and lender arrangement fees (£0–£2,000). The Mortgage Calculator UK helps you plan these costs.

Common Mistakes People Make When Getting a UK Mortgage

1. Focusing only on the monthly payment. A lower monthly payment on a longer term means paying significantly more interest overall. Always check the total repayment figure alongside the monthly amount.
2. Not comparing the total cost of different rates. A 2-year fix at 4.2% with a £999 fee might be cheaper overall than a 5-year fix at 4.5% with no fee — or vice versa. Use the calculator to compare total costs over the initial period.
3. Forgetting about lender arrangement fees. Some lenders charge £0–£999 arrangement fees, while others charge up to £2,000. These can be added to the loan amount (increasing your monthly payments and total interest) or paid upfront.
4. Ignoring early repayment charges (ERCs). Most fixed-rate mortgages have ERCs of 1–5% of the outstanding balance if you want to switch or pay off the mortgage during the fixed period. A 1% ERC on a £200,000 balance is £2,000.
5. Not getting a survey. A basic mortgage valuation from the lender only checks the property is worth what you are paying. A full building survey (Level 2 or 3) can uncover structural issues that cost thousands to fix.

Frequently Asked Questions

Conclusion

Getting a mortgage is one of the most complex financial decisions you will make, but understanding the numbers gives you the confidence to negotiate the best deal. Our Mortgage Calculator UK puts all the key information at your fingertips — monthly payments, total interest, stamp duty, and LTV ratio — in one instant result.

Your next steps:

1. Open the Mortgage Calculator UK and run your numbers right now.
2. Check your take-home pay with our Income Tax Calculator UK to confirm what you can afford.
3. If you are self-employed, estimate your tax bill with our Self Assessment Tax Calculator UK.
4. Get an Agreement in Principle from a lender or broker before you start viewing properties.