Understanding loan repayments and APR
Why your monthly payment stays the same but its makeup changes, what APR actually includes, and how overpaying really saves you money.
Written by Jack Dev · Last updated 2 October 2026
Every payment is part interest, part capital
Most loans — personal loans, car finance, repayment mortgages — work the same way: your monthly payment is fixed, but what it's actually made of shifts every single month. Interest gets charged on whatever you still owe, and that's at its highest right at the start, so early payments are mostly interest, barely denting the balance. As the balance shrinks, so does the interest charged on it, and later payments swing increasingly toward paying off capital instead.
APR isn't just the interest rate
APR bundles the interest rate and any mandatory fees into one yearly figure, specifically so loans with wildly different fee structures can actually be compared. A loan with a lower headline rate but a chunky arrangement fee can end up with a higher APR — and cost more overall — than one with a slightly higher rate and no fees. APR is the number worth comparing, not the rate on the poster.
One more thing worth knowing: advertised rates are usually 'representative', meaning at least 51% of successful applicants get that rate or better. Everyone else — often anyone with a thinner credit history — gets offered something worse once they actually apply.
Term length is a real trade-off, not just a bigger or smaller payment
Stretch the term and the monthly payment drops, which helps if affordability's tight — but you pay interest for longer, so the total cost climbs even though the rate hasn't moved an inch. A £10,000 loan at 6% APR costs about £1,601 in interest over 5 years, but roughly £2,276 over 7 — nearly £675 more, purely from stretching it out. Worth weighing that trade-off deliberately rather than just defaulting to the longest term on offer.
Overpaying works — but check for a penalty first
Because interest is charged on whatever's still outstanding, any overpayment shrinks the balance immediately, and every month after that you're charged interest on a smaller number. Pay extra early in the loan and you save more than paying the same extra amount later on. Just check first — many lenders cap penalty-free overpayments at around 10% of the balance a year, so a big lump sum could land you a fee.
Our Loan Repayment Calculator shows the fixed monthly payment and total interest for any amount, rate and term — worth running a couple of different term lengths to see the affordability-versus-cost trade-off for yourself.
Frequently asked questions
Interest is charged on whatever you still owe, which is highest right at the start of the loan — so early payments are mostly interest, and later payments shift increasingly toward capital as the balance falls.
No — APR bundles the interest rate with any mandatory fees into one yearly figure, which is why it's the number to compare between loans rather than the headline rate alone.
Yes, even at an identical rate, simply because you're paying interest on the outstanding balance for longer — a lower monthly payment over a longer term usually means more total interest by the end.
Generally yes, since overpaying shrinks the balance interest gets charged on. Check your loan agreement first, though — some lenders charge a fee above a certain overpayment amount.
This guide is general information, not financial or tax advice — check GOV.UK or a qualified adviser for anything that affects a real financial decision.