APR vs Interest Rate: What’s the Actual Difference?

APR vs Interest Rate: What’s the Actual Difference?

Two credit cards. One advertises “18.9% interest.” The other advertises “24.9% APR.” Most people assume the first one is cheaper. Often it isn’t, and the reason comes down to a distinction almost nobody explains properly at the point of sale.

APR and “interest rate” are not always the same number, and the gap between them can genuinely change which product is actually cheaper. Here’s what’s really going on.

The short version

The interest rate is the cost of borrowing the money itself, nothing else. APR, the Annual Percentage Rate, is meant to be the full annual cost of the credit, interest plus any compulsory fees, expressed as a single comparable figure. On a straightforward credit card with no annual fee, the interest rate and the APR often end up being close to the same number. On a loan with an arrangement fee, a mortgage with product fees, or a card with an annual charge, they can diverge meaningfully, and the APR is almost always the one that reflects what you’ll genuinely pay.

Why credit cards specifically use “representative APR”

UK credit advertising rules require lenders to display a “representative APR” whenever they advertise a rate. One important quirk worth knowing: a representative APR only has to be offered to 51% of people who are accepted for the product. That means nearly half of successful applicants could be offered a worse rate than the one advertised, and you won’t know which group you’re in until you actually apply and see your personal offer.

This is different from your personal purchase rate, which is the actual interest rate applied to your specific balance once you’re approved. On many standard credit cards, the purchase rate and the representative APR are identical or very close, because there’s no separate fee structure complicating the calculation. Where they diverge more is on cards with balance transfer fees, cash advance charges, or annual membership costs, since those get folded into the APR calculation on a representative basis but don’t always map cleanly onto what any individual cardholder experiences.

Where the gap actually costs you real money

Personal loans are where this distinction bites hardest. A loan advertising a 6.9% interest rate but charging a 2% arrangement fee added to the loan amount isn’t really a 6.9% product once you account for what you’re actually repaying relative to what you needed. The APR calculation folds that fee in and annualises it across the term, which is why two loans with identical headline interest rates but different fee structures can show meaningfully different APRs, and why comparing APR rather than the bare interest rate is the only way to genuinely compare two loan offers on equal terms.

Mortgages show the same pattern on a larger scale. A mortgage with a lower interest rate but a hefty product or arrangement fee can carry a higher APR, and therefore cost more overall, than a mortgage with a slightly higher rate and no fee, particularly on a shorter fixed term where the fee gets spread across fewer years of borrowing. Lenders are required to show you both figures specifically so this comparison is possible, but it only works if you actually look at the APR rather than anchoring on the headline rate that gets printed in bold on the advert.

Why store cards and catalogue credit often have the widest gap

Store cards and catalogue credit accounts frequently carry some of the highest representative APRs on the UK market, sometimes well above 25% or even 30%, considerably higher than a typical mainstream credit card. Because these accounts are often opened at the till during a purchase, in a moment focused on getting a discount on that day’s shopping rather than comparing borrowing costs, the APR gets far less scrutiny than it would if you were sitting down specifically to compare loan products. It’s worth treating a store card exactly the way you’d treat any other line of credit, checking the APR against your existing cards or a personal loan before signing up, rather than treating the in-store discount as the only number that matters.

Buy Now Pay Later products complicate this comparison further, since many short-term BNPL plans don’t display an APR at all, because they’re structured as fixed-fee or genuinely interest-free short-term credit rather than traditional revolving credit. That doesn’t make them automatically cheaper, it just means the APR comparison tool doesn’t apply cleanly, and you need to look at the actual total cost of the specific plan instead of assuming a lack of a quoted APR means a lack of cost.

A worked example

Say you’re comparing two £5,000 personal loans over three years. Loan A advertises a 7.9% interest rate with no fees. Loan B advertises a lower 6.9% rate but adds a £150 arrangement fee to the loan, so you’re actually repaying interest on £5,150 while only receiving £5,000 in your account. On the surface, Loan B looks cheaper because of the lower headline rate.

Run the actual numbers and the picture flips. Loan A costs £632 in total interest over the three years, £156.45 a month, APR 7.9% as advertised, since there’s no fee to distort the figure. Loan B costs £716 in total interest and fees for the same £5,000 actually received, £158.78 a month, and once you calculate the true annualised cost of what you borrowed against what you’re repaying, Loan B’s effective APR comes out at 8.91%, not the 6.9% printed on the advert, and higher than Loan A’s 7.9% despite having the lower headline rate. Loan A is the cheaper loan by roughly £84, the opposite of what the two interest rates alone would suggest.

What APR does not include

APR is a genuinely useful comparison tool, but it isn’t a complete picture of every cost you might face. Late payment fees, missed payment charges, early repayment charges on some fixed-term products, and optional add-ons like payment protection insurance generally sit outside the standard APR calculation. Two products with identical APRs can still end up costing very different amounts in practice if one has punishing late fees and the other doesn’t, so APR is the right starting point for comparison, not the final word on total cost if your circumstances might involve missing a payment or repaying early.

The one number worth actually anchoring on

When you’re comparing any two credit products, whether that’s two credit cards, two personal loans, or two mortgage deals, the APR is almost always the more reliable single figure to compare, precisely because it’s designed by regulation to fold fees and interest into one number specifically so products can be judged on equal terms. The interest rate alone tells you the cost of the money. The APR tells you closer to the cost of the whole deal. When they’re advertised separately and look meaningfully different, that gap is telling you something real about fees or charges baked into the product, not a marketing quirk to ignore.

Frequently asked

Why is my personal APR higher than the advertised representative APR?
Representative APR only has to be given to 51% of successful applicants. If your credit profile isn’t in the strongest tier the lender assesses, you may be offered a higher rate than the one advertised, even though you were still approved for the product.

Is a 0% purchase card’s APR really 0%?
During the promotional period, yes, genuinely 0%. The APR quoted for these cards, often around 24.9%, is the representative APR that applies after the 0% period ends, not the rate during the interest-free window itself. Always check what happens to your balance once the promotional period finishes.

Does a lower interest rate always mean a cheaper loan?
Not necessarily. If the lower-rate product carries a higher fee, or a shorter promotional structure, the APR, which accounts for both, can end up higher than a product with a slightly higher headline rate and no fees. Always compare APR rather than the bare interest rate when the two products have different fee structures.

What’s the difference between fixed and variable APR?
A fixed APR stays the same for a set period or the life of the agreement, giving you certainty over what you’ll pay. A variable APR can move up or down, usually in line with the Bank of England base rate or the lender’s own standard rate, meaning your repayments could change during the term.

Do all lenders calculate APR the same way?
The underlying formula is standardised by UK consumer credit regulation specifically so APR figures are comparable across different lenders and products. What varies is which fees a lender chooses to build into the headline product versus charge separately, which is why reading the full terms alongside the APR still matters.

Read more in our UK debt help hub, or explore our full library of free tools.

DebtShift is an educational platform. This content is for informational purposes only and does not constitute financial advice. For free, regulated debt advice contact StepChange at stepchange.org or call 0800 138 1111.