UK Mortgage Calculator 2026/27: Borrowing & Repayments

A UK mortgage calculator is most useful when you treat it as a planning worksheet rather than an approval engine. It can turn a property price, deposit, interest rate and term into an estimated loan-to-value ratio, monthly repayment and total interest. It can also show what happens if the rate is higher, the term is shorter or your deposit changes. That helps you decide which properties fit your cash flow before you pay for surveys, legal work or a full application.

It cannot promise that a lender will offer the amount on screen. MoneyHelper explains that affordability calculators use the information entered, while lenders apply their own criteria and request more detail. A formal assessment may consider income, regular spending, debts, credit history, dependants, employment, future changes and the lender’s rate assumptions. Use the Mortgage Calculator→ to organise those questions, then compare the output with an Agreement in Principle or lender illustration when you have one.

This guide explains the calculator workflow for 2026/27: what to enter, how to read borrowing power and LTV, how to test repayment risk, how buying costs change the deposit you can actually use, and which results should trigger a conversation with a lender or regulated adviser.

Key takeaways

What a mortgage calculator can and cannot tell you

The calculator can answer questions such as:

• What is the loan after my planned deposit?
• What is the loan-to-value ratio?
• What might the monthly repayment be at the rate I am testing?
• How would the payment change if the rate were higher or the term shorter?
• How much interest might I pay over the scheduled term?
• How much cash remains after an illustrative purchase-cost allowance?

The result is not a mortgage offer. It does not verify your payslips, inspect bank statements, search your credit file, assess variable income or match you to a lender’s underwriting policy. A model can also look optimistic if you leave out childcare, subscriptions, car finance, student-loan deductions, credit-card minimums or irregular annual bills. MoneyHelper says lenders consider household income, regular bills, debts and other spending, and may test whether you could keep paying if rates rise or your circumstances change.

The right interpretation is therefore: “This is what the deal looks like under these assumptions.” It is not: “This is what a bank must lend me.” Keep the assumptions beside the result when you save or compare scenarios.

Step 1: set the property price and usable deposit

Enter the price of the property you are considering and the deposit you can actually commit. The basic relationship is:

For example, a £300,000 property with a £45,000 deposit implies a £255,000 loan and an 85% LTV. If you have £45,000 in savings but need £8,000 for tax, conveyancing, a survey, removals and a cash reserve, entering the full £45,000 as deposit overstates the purchase price you can safely target. Run a “maximum cash” scenario and a “protected reserve” scenario separately.

A larger deposit usually reduces the amount borrowed and the LTV. That can affect product availability and pricing, but it is not a guarantee of acceptance. A lender can still decline or reduce the loan after assessing income, expenditure, credit history, property type and its own policy. Avoid using the calculator to bid up to the maximum price simply because the deposit produces a lower LTV.

Step 2: enter gross income, then challenge the income assumption

The calculator may use gross annual income to create an illustrative borrowing-power ceiling. That is useful for orientation, but lenders do not all treat income the same way. Basic salary, overtime, commission, bonuses, self-employed profit, benefits and second-job income can have different evidence and averaging requirements.

MoneyHelper says lenders work out household income and may include income from employment, freelancing, benefits, commission or bonuses. It also says the detailed affordability process considers bills, spending and debts. Enter only income you could document and explain. If variable income is important to the purchase, create a conservative scenario that excludes it or includes only the portion a lender has confirmed it will use.

The familiar “4.5 times income” calculation is a rough reference, not an individual entitlement. MoneyHelper describes four-and-a-half times annual income as a usual cap, but says it is not guaranteed. The Bank of England’s separate loan-to-income framework is an aggregate lending constraint, not a promise that every applicant can borrow that multiple. A £50,000 salary multiplied by 4.5 gives £225,000 as a mathematical illustration; it does not establish that £225,000 is affordable for a particular household.

Step 3: record outgoings and debts before trusting the result

The mortgage amount that fits the income multiple may not fit the monthly budget. Add recurring spending before comparing properties:

Some lenders use detailed bank-statement analysis; others apply standardised household-cost assumptions. Your calculator cannot reproduce every lender’s model. Its purpose is to expose the budget pressure that a headline salary multiple hides. If the payment only works when groceries, transport or annual bills are missing, the scenario is not affordable just because the calculator returns a green result.

Also consider what changes after completion. A first child, reduced working hours, retirement, a new commute or the end of a fixed-rate deal may change affordability. MoneyHelper notes that lenders may stress whether payments remain manageable if rates rise or circumstances such as retirement, maternity leave or having a child occur.

Step 4: understand the repayment calculation

For a standard repayment mortgage, each monthly payment contains interest and a capital repayment. At the start, the interest portion is usually larger because the outstanding balance is highest. As capital falls, the interest portion reduces. The calculator can therefore show both the monthly payment and the total scheduled interest, but the result depends on the rate remaining unchanged for the modelled period.

The term matters. A 25-year term usually produces a higher monthly payment than a 35-year term for the same loan and rate, but the shorter term can reduce total interest if all payments are made as scheduled. A longer term may improve the initial monthly figure while extending the period during which interest is charged. Compare both the monthly result and the lifetime interest estimate, then ask whether the term remains suitable for your age, income plan and lender eligibility.

Interest-only is a separate decision. MoneyHelper says not all lenders offer it and an applicant needs a credible repayment method as well as meeting income criteria. Do not compare an interest-only payment with a repayment-mortgage payment as if they were equivalent: the former may leave the capital outstanding and requires a realistic plan to repay it.

Step 5: run rate scenarios, not just one headline rate

Enter the rate attached to the product you are considering, but do not present it as a live quote unless it came from a lender or broker under stated eligibility conditions. Then run clearly labelled sensitivity cases. For example:

The existing Mortgage Stress Test guide explains why there is no universal 2026/27 rule requiring every lender to add three percentage points to the rate. Use the scenarios to ask a practical question: “Could the household still pay if the rate at a future product change or reversion period were materially higher?” The answer should include food, energy, Council Tax, insurance, childcare and debt payments, not just the mortgage line.

Fixed and variable products behave differently. MoneyHelper explains that a fixed rate stays the same during the fixed period, while a variable rate can change and a tracker usually follows another rate. A fixed payment can still change when the deal ends. A tracker or standard variable rate can change sooner. Model the rate path you understand, and read the lender’s illustration for the actual reversion rate, fees, early repayment charges and APRC.

Step 6: use LTV and affordability together

LTV is a property-risk and product comparison measure; it is not a complete affordability measure. Two households can have the same 75% LTV and very different capacity because their income, debts and dependants differ. Conversely, a high income does not make a large loan safe if the monthly payment leaves no resilience.

Use three linked views:

1. Cash view: deposit, tax, fees and reserve after completion.
2. Income view: net household income after realistic deductions and committed spending.
3. Rate view: payment at the deal rate and at alternative rates.

If any view fails, lower the target price or loan, increase the deposit only if the reserve remains intact, reduce commitments where appropriate, or delay the purchase while building resilience. Extending the term can reduce the scheduled payment but increases the time and potential interest cost. It should not be used to hide a monthly deficit.

Step 7: add purchase costs and location correctly

The mortgage is only one part of the completion budget. MoneyHelper advises budgeting for solicitor fees, Stamp Duty and other costs in addition to monthly payments. For a purchase in England or Northern Ireland, the calculator can use an illustrative Stamp Duty Land Tax amount based on the current residential rates and buyer circumstances. Check the Stamp Duty Land Tax guide and the official GOV.UK rates before relying on a figure.

Do not use an England-and-Northern-Ireland SDLT result for a Scottish or Welsh purchase. Scotland has Land and Buildings Transaction Tax and Wales has Land Transaction Tax, with different administration and rules. First-time buyer relief, an additional-property surcharge, non-UK-resident rules and transaction structure can also change the result. If the calculator does not cover the relevant jurisdiction or status, leave the amount as a separate research item rather than treating zero as confirmed.

Other costs can include valuation or survey work, conveyancing, broker fees, lender product fees, insurance, removals, repairs and furnishing. Some can be added to a loan in certain products, but borrowing them increases interest and may affect LTV. Keep a cash buffer after completion; a property that uses every pound of savings can be fragile even when the mortgage payment passes a simplified test.

Step 8: turn the result into an application checklist

MoneyHelper lists documents that may be requested, including payslips, bank statements, proof of deposit, identity documents and, for some self-employed applicants, accounts or tax-return evidence. Prepare accurate records and make sure the figures in an application match the documents. A calculator is most valuable when it helps you notice missing evidence before the application, not when it encourages you to round income up or omit costs.

Common questions

Run the Mortgage Calculator→ with a base case, a protected-cash case and higher-rate scenarios. Then compare the output with the Mortgage Stress Test guide, the Moving House Costs guide and the official sources below before committing to an offer.

Official sources

• MoneyHelper — How much can I borrow?
• MoneyHelper — How to apply for a mortgage
• FCA — Getting a mortgage: the rules that affect you
• MoneyHelper — Understanding mortgages and interest rates
• GOV.UK — Stamp Duty Land Tax residential property rates

This guide is educational and does not provide mortgage, tax, legal or financial advice. Calculator results are estimates based on stated assumptions and do not constitute a lender decision, mortgage offer, Agreement in Principle or regulated recommendation.