How much can I borrow? Mortgage affordability explained
One of the first things most buyers want to know is how much a lender will actually let them borrow. It is a natural question, you need a rough figure before you can start looking at properties with any confidence.
The honest answer is that it depends on more than just your income. Lenders use a combination of income multiples, affordability assessments, and stress tests to arrive at a number. Understanding how these work will give you a much clearer picture of where you stand, and help you avoid the frustration of falling in love with a property that turns out to be just out of reach.
The income multiple: a starting point, not the whole picture
For many years, the simplest way to estimate how much you could borrow was to multiply your annual income by a set number. Traditionally, lenders used a multiple of around 3.5 times your gross income, or, for joint applications, 3.5 times your combined income.
That figure has shifted upward over time. Many lenders now offer multiples of 4 to 4.5 times income as standard, and some will go to 5 or even 5.5 times for borrowers who meet certain criteria, typically those with higher incomes, strong credit profiles, or smaller loan to value ratios.
A useful rule of thumb for a first estimate: take your annual salary, multiply it by 4 to 4.5, and you have a rough indication of what a lender might offer. On a single income of £45,000, that suggests a borrowing range of roughly £180,000 to £202,500. On a combined income of £75,000, the range rises to £300,000 to £337,500.
But this is only the starting point. The income multiple is a ceiling, not a guarantee.
Affordability assessment: the real test
In 2014, following the financial crisis, the Financial Conduct Authority introduced stricter rules requiring lenders to go beyond income multiples and carry out a full affordability assessment before approving a mortgage. These rules remain in place today.
An affordability assessment looks at your whole financial picture. Income is part of it, but so are your outgoings.
Lenders will typically ask about or verify the following:
- Your regular financial commitments. This includes credit card minimum payments, personal loan repayments, car finance, student loan deductions, and any other fixed monthly obligations. These reduce the amount of your income that a lender considers available to service a mortgage.
- Your day to day living costs. Some lenders use their own statistical models for this, while others ask you to declare your spending on things like food, transport, childcare, and subscriptions. The figures used vary between lenders, which is one reason why different lenders can arrive at quite different borrowing limits from the same application.
- Childcare costs. If you have children in paid childcare, this is a significant monthly outgoing that lenders factor in heavily. It can substantially reduce your borrowing capacity compared to a household with the same income but no childcare costs.
- Any dependants. The number of children or other financial dependants in your household affects the assumed cost of living that lenders apply to your assessment.
The stress test: can you afford it if rates rise?
Beyond your current income and outgoings, lenders are also required to assess whether you could still afford your mortgage if interest rates were to rise significantly.
This is called a stress test. The lender takes the interest rate on the mortgage you are applying for and tests your affordability at a higher notional rate, typically 2% to 3% above your actual rate, though the exact approach varies between lenders.
If the monthly payment at the stressed rate would push your finances beyond what the lender considers sustainable, they may reduce the amount they are willing to lend, even if you could comfortably afford the actual payment at today's rate.
This is why the figure a lender offers you can sometimes be lower than the income multiple would suggest. The stress test is a significant factor for many borrowers, particularly when interest rates are already elevated.
Why a broker's number and a bank's number can differ
If you use a mortgage calculator on a bank's website, you get one figure. If you speak to a whole of market mortgage adviser, they may come up with a different, sometimes higher, number from a different lender. Both can be accurate.
The reason is that lenders set their own criteria, and those criteria vary quite significantly. One lender may include 100% of a bonus when calculating your income. Another may only use 60%. One may treat student loan repayments as a major deduction; another may apply a lower impact. One may be comfortable lending to a contractor on a day rate; another may require two years of accounts.
These differences mean that your maximum borrowing capacity is not one fixed number. It is specific to you, your income structure, your outgoings, and which lender is doing the assessment.
A mortgage adviser who knows the market well understands how different lenders assess different types of income and can direct you toward the one most likely to offer you the best deal for your circumstances.
What can you do to improve your borrowing capacity?
If the figure you are being quoted feels lower than you hoped, there are a few levers worth considering.
- Reduce your outstanding credit balances. High credit utilisation and large outstanding balances on credit cards and loans reduce your assessed affordability. Paying these down before applying can make a meaningful difference.
- Clear or reduce any regular financial commitments. A £250 per month car finance payment can reduce your maximum borrowing by as much as £50,000 in some lenders' assessments. If you are coming to the end of a finance agreement, completing it before applying is worth doing.
- Apply jointly. Adding a second income to an application, a partner, for example, increases the total income against which the multiple is applied. This can open up a significantly higher borrowing limit.
- Consider a longer mortgage term. Stretching your mortgage term from 25 to 30 or 35 years reduces the monthly payment, which can help you pass the stress test at a higher loan amount. You pay more in total interest over time, but it gives you access to a higher borrowing limit if affordability is tight.
What lenders will not tell you on the phone
One thing worth knowing is that the figure a lender quotes on an initial call or through an online calculator is often higher than what they will actually approve at the underwriting stage. Calculators and indicative figures do not verify your income, they take you at your word.
When your full application is submitted and your payslips, bank statements, and documentation are reviewed, the actual offer can sometimes come in lower. This is not common for straightforward cases, but it does happen, particularly if there are complexities around income, credit history, or outgoings that were not fully captured in the initial assessment.
This is another reason why speaking to an adviser before you start making offers on properties is valuable. A good adviser will take a thorough look at your situation upfront, identify any potential issues, and give you a realistic picture of what you are likely to be approved for, not just what a calculator says.
The short version
Your mortgage borrowing capacity is determined by your income, your financial commitments, your credit profile, and the stress testing criteria of the lender you apply to. Income multiples give you a rough starting point, but the affordability assessment and stress test are what ultimately determine the offer. Different lenders assess the same application differently, which is why a whole of market adviser can often find you a higher borrowing limit than you would get by going directly to a single bank.
If you want a clear and realistic figure before you start your property search, an adviser can give you one, based on your actual circumstances, not a generic calculator.
This article is for informational purposes only and does not constitute financial advice. Always speak to a qualified mortgage adviser before making decisions about borrowing.