Mortgage Repayment Calculator 2026
Calculate your monthly payment, total interest, and full amortisation schedule
Borrowing check
Stress-test rate, term and deposit assumptions before comparing mortgage deals or remortgage options.
How to use
- ✓Enter your details in the calculator
- ✓Results update instantly as you type
- ✓2026/27 assumptions already included
Disclaimer
Results are estimates based on HMRC published rates. Individual tax codes, benefits-in-kind, and other factors may affect your actual liability. Consult a qualified accountant for personal advice.
UK Mortgage Repayment: The Complete 2026/27 Guide
A mortgage is the largest financial commitment most people ever make. Understanding how mortgage repayments are calculated — and how small changes to rate, term, or deposit size can impact total cost by tens of thousands of pounds — puts you in a position to make genuinely informed decisions about one of the most important financial moments of your life.
This guide covers everything: the mathematics of mortgage repayment, how amortisation works, the profound impact of interest rate changes, the long-term cost of extending your term, and practical strategies for reducing the total amount you pay. Each section uses real numbers based on your inputs above.
Amortisation: How Your Balance Falls Over Time
Amortisation describes the process by which your loan balance reduces over the term. In the early years of a repayment mortgage, the majority of your monthly payment covers interest — leaving very little to reduce the actual debt. As the balance falls, more of each payment goes to capital. This is why the first few years of a mortgage feel slow in terms of equity building, while the final years are significantly faster.
How Interest Rate Changes Your Monthly Payment
Even a 1% change in interest rate has a dramatic effect on both monthly payments and total interest paid. The chart below shows monthly payments and total interest across different rate scenarios for your current loan amount of £300,000.00 over 25 years.
| Rate | Monthly Payment | Total Interest | vs Current |
|---|---|---|---|
| 3% | £1,423.00 | £126,790.00 | -£419.00/mo |
| 3.5% | £1,502.00 | £150,561.00 | -£340.00/mo |
| 4% | £1,584.00 | £175,053.00 | -£258.00/mo |
| 4.5% | £1,667.00 | £200,249.00 | -£175.00/mo |
| 5% | £1,754.00 | £226,131.00 | -£88.00/mo |
| 5.5% | £1,842.00 | £252,679.00 | ← current |
| 6% | £1,933.00 | £279,871.00 | +£91.00/mo |
| 6.5% | £2,026.00 | £307,686.00 | +£184.00/mo |
| 7% | £2,120.00 | £336,101.00 | +£278.00/mo |
| 7.5% | £2,217.00 | £365,092.00 | +£375.00/mo |
Shorter vs Longer Term: The True Cost of Extra Years
Extending your mortgage term reduces monthly payments — but massively increases the total interest paid. The chart below makes this trade-off visible across different term lengths for your loan.
| Term | Monthly | Total Interest | Total Repaid |
|---|---|---|---|
| 15 yrs | £2,451.00 | £141,225.00 | £441,225.00 |
| 20 yrs | £2,064.00 | £195,279.00 | £495,279.00 |
| 25 yrs | £1,842.00 | £252,679.00 | £552,679.00 |
| 30 yrs | £1,703.00 | £313,212.00 | £613,212.00 |
| 35 yrs | £1,611.00 | £376,641.00 | £676,641.00 |
Overpayments: The Power of Paying More
Mortgage overpayments are one of the most effective guaranteed returns available to UK homeowners. Every extra pound you pay reduces the principal, which in turn reduces the interest charged in subsequent months. Because interest compounds over time, early overpayments have an outsized effect compared to later ones.
| Monthly Overpayment | Interest Saved | Years Saved | New Term |
|---|---|---|---|
| +£100.00/mo | £28,267.87 | 2.5 years | 22y 6m |
| +£200.00/mo | £52,324.44 | 4.6 years | 20y 5m |
| +£300.00/mo | £70,669.69 | 6.3 years | 18y 9m |
| +£500.00/mo | £98,279.82 | 8.8 years | 16y 2m |
| +£750.00/mo | £122,363.17 | 11.2 years | 13y 10m |
| +£1,000.00/mo | £140,550.68 | 12.9 years | 12y 1m |
Types of UK Mortgages and When to Use Each
Fixed Rate (2-5 years)
Pros: Predictable payments, rate protection
Cons: ERCs if you exit early, may be higher than tracker
Best for: First-time buyers, those who value certainty
Tracker Mortgage
Pros: Falls if base rate drops, no ERCs typically
Cons: Payments rise if base rate rises
Best for: Borrowers who expect rates to fall
Offset Mortgage
Pros: Savings reduce interest without reducing flexibility
Cons: Usually higher rate than equivalent fixed
Best for: Those with significant savings alongside mortgage
Interest-Only
Pros: Lower monthly payments
Cons: Capital never reduces — need repayment plan
Best for: Buy-to-let investors, specific situations
Frequently Asked Questions
How is my monthly mortgage payment calculated?
Using the standard amortisation formula: P × [r(1+r)^n] / [(1+r)^n - 1], where P is principal, r is monthly rate, and n is number of payments. This ensures equal payments throughout the term while gradually shifting the ratio from interest to capital repayment.
What is LTV and why does it matter?
LTV (Loan-to-Value) is your mortgage as a percentage of the property's value. A £180,000 mortgage on a £300,000 property = 60% LTV. Lower LTV = lower risk for the lender = better interest rate. Every 5% reduction in LTV typically unlocks a better rate tier.
Can I port my mortgage when I move?
Most fixed-rate mortgages are portable — you can take your current rate to a new property. If you need to borrow more, the additional amount is at a new rate. Some lenders impose conditions on portability.
What is an ERC (Early Repayment Charge)?
A penalty fee charged if you repay more than the allowed overpayment allowance (typically 10%/year) or exit the deal before the fixed term ends. ERCs are usually expressed as a percentage of the outstanding balance and decline each year.
How does the Bank of England base rate affect my mortgage?
Tracker and variable rate mortgages move directly with the base rate. Fixed rate mortgages are insulated until the deal ends. When rates are expected to fall, trackers and shorter fixes become more attractive. When rates are expected to rise, longer fixed rates offer protection.
How to use the Mortgage Repayment Calculator properly
The Mortgage Repayment Calculator is built for mortgage and property planning. It is designed to turn a complex financial question into a clear working estimate using 2026/27 assumptions. The headline result is useful, but the real value comes from understanding which inputs drive the answer, which thresholds matter, and which linked tools should be checked before making a decision.
This calculator is most useful when you treat it as the first step in a decision chain. Enter realistic values, review the assumptions, then follow the internal links to related calculators and guides. For example, a salary calculation may need a second check against income tax, National Insurance, student loans and pensions. A property calculation may need a second check against stamp duty, mortgage affordability, rental yield and capital gains tax. A business calculation may need to connect corporation tax, VAT, employer NI and dividend tax.
The 2026/27 UK tax and finance environment makes this joined-up approach important. Frozen thresholds mean more earnings are pulled into tax over time. Employer National Insurance remains a major cost above the secondary threshold. Pension contributions, salary sacrifice, student loans and regional tax differences can all change the final answer. A calculator that only shows one number can miss the bigger picture; a calculator supported by internal guides and related tools helps users understand the full decision.
Typical uses
Start with clean inputs
Use the best available numbers for monthly repayments, affordability, stamp duty, rental yield, interest rates, remortgaging and long-term property costs. Avoid mixing annual and monthly figures, and check whether a figure should be gross, net, pre-tax or post-tax.
Check the assumptions
Results are estimates. They cannot know every payroll code, lender rule, company policy, benefit-in-kind, local tax variation or personal circumstance unless those details are entered or explained.
Sense-check the outcome
Compare the result against your payslip, lender example, budget or tax estimate so you know whether one assumption needs adjusting before you rely on it.
What affects the result?
Several variables can move the final result more than users expect. Tax year thresholds affect the point at which deductions begin. Pension contributions can reduce taxable income but also reduce immediate cash flow. Student loans are calculated using their own thresholds and rates. Salary sacrifice can save income tax and National Insurance but may affect pensionable pay, mortgage affordability or employer benefits. For property calculations, interest rates, term length, fees and deposit size can change the result by thousands of pounds. For business calculations, the interaction between salary, dividends, VAT, corporation tax and National Insurance is often more important than any single rate.
This is why the page includes both a calculator and supporting content. A user looking for a quick estimate can get one instantly. A user making a real decision can continue into the linked guides, compare adjacent tools and understand what the numbers mean. Good internal linking also helps search engines understand the topic relationship between pages: calculators answer transactional queries, while guides answer explanatory queries.
Worked example workflow
A strong workflow starts with a base case. Enter the most likely values first: the salary you expect, the mortgage amount you are considering, the loan term you are comparing, the savings contribution you can afford, or the business profit you expect to make. Record the result, then change one input at a time. This makes it clear which variable is doing the most work.
For a pay calculation, compare the base salary against a scenario with pension salary sacrifice, a scenario with student loan repayments, and a scenario with a bonus or overtime. For a property calculation, compare the current rate against a higher-rate stress test, then shorten or lengthen the term to see the lifetime interest effect. For a business calculation, compare profit extraction methods and then check the connected tax pages. This approach turns a single estimate into a decision framework.
The important point is to avoid changing several assumptions at once. If a result improves, you need to know whether the improvement came from a higher deposit, a lower interest rate, a pension contribution, a tax band change or a different repayment term. The calculator gives the number; the comparison gives the insight.
2026/27 checklist before relying on the result
- Check the tax year: use 2026/27 figures when comparing current salaries, payroll deductions, property taxes or business profits.
- Check the basis: confirm whether an input should be annual, monthly, weekly, gross, net, pre-tax, post-tax or pensionable.
- Check location: Scotland can use different income tax bands, and property taxes differ between England, Scotland and Wales.
- Check deductions: pension, student loans, salary sacrifice, benefits and allowances can all materially alter the result.
- Check related pages: use the internal links on this page to test the decision from a second angle before acting.
How this calculator connects to the wider financial picture
Income and affordability
A calculator result is often used by another decision. Net income affects mortgage affordability, household budgets, emergency fund targets and loan repayment capacity. Gross income affects tax bands, pension contributions, student loan repayments and child benefit. If the page you are using changes an income figure, it is sensible to follow through to the take-home pay, mortgage affordability and budgeting tools.
Tax and timing
Many UK thresholds are annual, but most real-life decisions are monthly. PAYE deductions, mortgage payments, rent, bills and loan repayments are usually felt month by month. A yearly saving can look large until divided by twelve; a monthly cost can look small until multiplied across a full year or mortgage term. The best use of the calculator is to compare both annual and monthly effects.
Risk and sensitivity
The result is only as stable as the assumptions behind it. Interest rates, pay awards, inflation, house prices, bonuses, overtime, profit margins and tax policy can all change. Run a conservative version, a central version and an optimistic version. If the decision only works in the optimistic version, it probably needs more caution.
Record keeping
Keep a note of the assumptions you used, especially for tax, business and mortgage decisions. If your tax code changes, your pension percentage changes, your company profit changes or a lender offers a different rate, rerun the calculation. The internal guides explain the rule changes and the calculators show the numerical impact.
Frequently asked questions about this type of calculator
Is the result exact?
No online calculator can cover every personal circumstance, but it can give a strong planning estimate when the right inputs are used. Use payslips, lender illustrations, HMRC notices or accounting records where possible.
Why does my real result differ?
Differences usually come from tax codes, pension scheme rules, student loan plans, benefits-in-kind, regional tax differences, fees, timing or incomplete input data.
Should I use annual or monthly figures?
Use whatever the calculator asks for. If a field says annual salary, enter the annual gross figure. If a field asks for monthly payment, enter the monthly amount. Mixing periods is the most common source of errors.
What should I do after calculating?
Use the related calculators and guides to test the same decision from another angle, then confirm important choices with payroll, an accountant, a broker or another qualified professional where needed.
How to interpret the result in 2026/27
Short-term cash flow
The monthly result tells you what the decision feels like in real life. For income pages, that means money available after deductions. For mortgage and debt pages, it means the recurring payment. For savings pages, it means the commitment required to hit a target. Monthly affordability should be tested against bills, food, transport, insurance, subscriptions and emergency savings rather than judged in isolation.
Annual tax impact
The annual result shows the tax-year impact. Frozen allowances and thresholds mean the annual view is especially important in 2026/27. It helps identify whether income crosses the higher-rate threshold, whether allowances taper, whether a student loan plan becomes active, or whether a business profit level changes the corporation tax position. Annual numbers also make it easier to compare job offers and investment decisions.
Lifetime cost or benefit
Some decisions look small monthly but large over time. A slightly higher mortgage rate can add tens of thousands over the term. A pension contribution can reduce take-home pay today but build long-term retirement income. A debt repayment change can shorten or lengthen the payoff date. Use the result as a starting point, then check the total cost or total benefit where the calculator provides it.
The goal is not just to display a result, but to help users make better financial decisions. Each calculator page therefore includes supporting explanation, internal links, related calculators and related guides. That structure gives every page enough context to stand alone while also encouraging users to explore the wider topic cluster. It also mirrors how people actually make financial decisions: they calculate, compare, learn, adjust assumptions and calculate again.
Further reading
Stamp Duty Calculator
Compare the result against a closely related calculator.
Mortgage Affordability Calculator
Compare the result against a closely related calculator.
Types of UK Mortgages Explained 2026/27: Fixed, Tracker, Offset and More
A plain-English guide to every type of UK mortgage and how to choose the right one in 2026/27.
Stamp Duty Guide 2026/27: SDLT Rates, First-Time Buyer Relief and More
Complete guide to stamp duty land tax in England, LTT in Wales, and LBTT in Scotland for 2026/27.
Common mistakes to avoid
Do not compare gross figures with net figures. Do not assume a pay rise turns into the same percentage increase in take-home pay. Do not ignore pension, student loan or salary sacrifice deductions. Do not use a mortgage repayment result as a full affordability assessment. Do not make a company director decision by looking only at dividend tax. The right answer normally depends on combined effects.
The best workflow is to run the calculator, read the explanation, then use at least one related calculator and one related guide. This gives a practical answer and a stronger understanding of the rules behind it.
Decision rule
Run a base case, then rerun with one changed assumption. If the answer changes materially, the decision needs a second check before you act.
Related Guides
Types of UK Mortgages Explained 2026/27: Fixed, Tracker, Offset and More
A plain-English guide to every type of UK mortgage and how to choose the right one in 2026/27.
Stamp Duty Guide 2026/27: SDLT Rates, First-Time Buyer Relief and More
Complete guide to stamp duty land tax in England, LTT in Wales, and LBTT in Scotland for 2026/27.
UK Monthly Budgeting Guide 2026: Build a Plan That Actually Works
How to build a monthly budget for UK salaries in 2026 — frameworks, average costs, and practical strategies.
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