How a personal loan repayment is worked out
Almost every UK personal loan is an amortising loan, which means each monthly repayment is the same fixed amount for the whole term, but the mix inside that payment changes over time: early payments are weighted more heavily towards interest, and later payments increasingly pay down the capital you originally borrowed. The calculator above uses the standard amortisation formula, taking your loan amount, annual interest rate and term in months, to work out the fixed monthly payment, the total you'll repay over the full term, and therefore the total interest cost of the loan.
Why the advertised APR isn't always your rate
UK lenders are required to advertise a "representative APR" — the rate that at least 51% of successful applicants are actually offered. That means up to 49% of people who take out the loan pay a different rate, sometimes considerably higher, based on their own credit profile. This is a common source of frustration: someone applies expecting the advertised rate, only to be offered something less attractive once the lender has assessed their file. It's worth treating any advertised APR as a rough guide to the lender's pricing rather than a guaranteed personal rate, and using a soft-search eligibility checker where available, since this shows you a likely rate without leaving a mark on your credit file the way a full application does. Our guide to soft and hard credit searches explains the difference in more detail.
How term length changes the total cost
Stretching a loan over a longer term reduces the monthly payment, which can make it feel more affordable, but it increases the total interest paid overall, because you're carrying a balance (and therefore accruing interest) for longer. Shortening the term has the opposite effect: higher monthly payments, but a lower total cost. There's no universally "right" answer here — it depends on what monthly payment comfortably fits your budget without straining it, balanced against how much extra you're willing to pay in total interest for that lower monthly commitment. Running the numbers at a couple of different term lengths using the calculator above is a quick way to see the trade-off for your own loan amount and rate.
Fixed rate, fixed term: what makes personal loans predictable
Unlike credit cards or overdrafts, most UK personal loans are structured with a fixed interest rate for the whole term, which means your monthly payment doesn't change once the loan is agreed, regardless of what happens to the Bank of England base rate or wider market conditions afterwards. This predictability is one of the main reasons people choose a personal loan over other forms of borrowing when consolidating debt or funding a large one-off purchase — you know exactly what you'll pay each month and exactly when the loan will be cleared, which makes budgeting considerably easier than with variable-rate borrowing. Our full guide to personal loans covers eligibility, secured versus unsecured options, and early repayment rules in more depth.
Early repayment and the rule of 78
If you come into some money and want to clear a personal loan early, UK consumer credit rules generally entitle you to a rebate of some of the interest you would otherwise have paid, though lenders are also allowed to charge a small early settlement fee, typically capped by regulation. Historically, some lenders used a method called the "rule of 78" to calculate how much interest you'd saved by repaying early, which front-loads interest more aggressively than a simple daily-interest calculation — meaning early repayment in the first year or two of the loan sometimes saves less than you might expect. Most modern loans use simple daily interest instead, which is more favourable to early repayment, but it's worth checking your specific loan agreement rather than assuming.
Using this alongside other borrowing decisions
A loan repayment calculator is most useful as a comparison tool: run the same amount through a few different rate and term combinations from different lenders' quotes, and you can see immediately which offer genuinely costs less overall, rather than comparing headline monthly payments in isolation, which can be misleading if the terms differ. If you're weighing a personal loan against consolidating several existing debts into one, our debt consolidation calculator runs a similar comparison specifically for that scenario, and our true cost of borrowing calculator adds arrangement fees into the picture for a fuller like-for-like comparison.