Loan Affordability Calculator
Most loan calculators work forwards — enter an amount, a rate and a term, and see the monthly payment. This one works the other way round: enter what you can genuinely afford to pay each month, and it works backwards to show the maximum loan that payment could realistically support, which is often the more useful question when you do not yet know how much you actually want or need to borrow.
Loan Affordability Calculator
Find out the maximum loan amount you could afford based on your income and outgoings.
Working Backwards From What You Can Afford
This calculator takes your maximum comfortable monthly payment and reverses the standard loan repayment formula to find the loan amount that payment would service at a given rate and term — the same maths lenders use to calculate a monthly payment from a loan amount, simply run in the opposite direction. This is a genuinely more grounded way to approach borrowing than starting with a target amount and hoping the resulting payment happens to fit your budget, since it starts from what is actually affordable and lets the loan size follow from that, rather than the other way around.
This distinction matters most for anyone comparing options, such as a car or a home improvement, where the actual cost is somewhat flexible — knowing the maximum affordable loan first can shape realistic choices, rather than committing to a specific price and only discovering afterward that the resulting payment does not comfortably fit the budget.
Why 35% Is the Number, Not 50% or 100%
This calculator caps the maximum monthly loan payment at 35% of your gross monthly income, a deliberately conservative figure rather than the maximum a lender might theoretically approve. This leaves meaningful room for other essential costs, existing commitments, and simply living, rather than stretching to the absolute limit of what a lender’s own criteria might allow. Lenders themselves generally look at overall debt-to-income ratios well below 100%, but their specific thresholds vary and can be less conservative than the deliberately cautious figure used here — this calculator is designed to suggest a comfortable borrowing level, not the maximum theoretically obtainable one.
Treating this 35% figure as a sensible ceiling rather than a target to reach is worth keeping in mind — a lower monthly commitment than the maximum suggested here leaves genuine breathing room for unexpected costs, which matters more in practice than maximising how much can technically be borrowed.
Disposable Income Is the Real Starting Point, Not Salary
The calculation starts from your monthly income, then subtracts your existing committed monthly outgoings — rent or mortgage, other loan repayments, regular bills — before applying the 35% affordability cap to what remains, not to your gross income directly. This matters considerably: someone with high existing commitments has meaningfully less genuine capacity for new borrowing than someone on the same salary with few existing outgoings, even though a calculation based on income alone would suggest identical affordability for both. Entering your outgoings accurately, rather than leaving the field at zero, is the single most important thing for getting a realistic result here.
It is worth going through a recent bank statement to list actual committed monthly outgoings rather than estimating from memory, since underestimating this figure is one of the most common ways a result here ends up more optimistic than a genuinely realistic affordability picture would suggest.
Seeing the Formula Run in Reverse
On a £42,000 salary with £900 of monthly committed outgoings, monthly income works out to roughly £3,500, leaving £2,600 of disposable income once outgoings are subtracted. Capping the maximum loan payment at 35% of that disposable figure gives roughly £910 a month available for a new loan. At 9.9% APR over three years, that £910 monthly payment supports a maximum loan in the region of £28,200 — the reverse-engineered answer to “how much could this payment actually borrow.”
What This Doesn’t Tell You
This calculator estimates affordability based on your own numbers, but it does not check your credit score, verify your income, or reflect any individual lender’s specific underwriting criteria, all of which genuinely affect what a lender would actually offer. A strong affordability position on paper does not guarantee approval if your credit history does not meet a lender’s requirements, and conversely, a specific lender might approve less, or occasionally more, than this estimate depending on their own risk appetite. Once you have a realistic affordability figure, our Personal Loan Calculator lets you model the actual monthly payment for a specific loan amount and rate, and our Loan Eligibility Checker gives an indication of approval likelihood based on credit-related factors this calculator does not consider.
Frequently Asked Questions
Should I borrow the maximum this calculator suggests?
Not necessarily — this shows a reasonable ceiling based on your numbers, not a target to aim for. Borrowing less than the maximum leaves more financial flexibility and reduces total interest paid over the loan’s term.
Does this account for future changes to my income or outgoings?
No — it reflects your current situation only. If you expect a significant change, such as a mortgage starting or income reducing, it is worth running the calculation again with those adjusted figures rather than relying on today’s numbers for a longer-term borrowing decision.
Why might a lender offer me less than this estimate?
Lenders factor in your credit history, existing credit commitments visible on your credit file, and their own specific risk appetite, none of which this calculator has access to, so an individual lender’s actual offer can reasonably differ from this general estimate.
Does the interest rate I enter affect the result significantly?
Yes, meaningfully — a lower rate allows a larger loan for the same monthly payment, since less of each payment goes toward interest, so it is worth using a realistic rate based on your likely credit profile rather than the most optimistic rate advertised.
Is a shorter or longer term better for affordability?
A longer term generally supports a larger loan for the same monthly payment, since the amount is spread over more months, though it also means paying more total interest over the life of the loan — a trade-off worth weighing rather than automatically choosing the longest available term.
Important Information
This calculator provides an estimate based on the figures you enter and does not constitute financial advice or a lending decision. Actual affordability and loan offers depend on individual lender criteria and a full credit assessment. For advice specific to your circumstances, consult a qualified financial adviser. See our Disclaimer for further information.