APR and the true cost of borrowing
APR is the single most useful number for comparing loans — but it's widely misunderstood. This guide explains what APR includes, how representative APR works, and how to use it to find the cheapest deal.
What APR actually measures
The Annual Percentage Rate expresses the total cost of a loan — the interest plus any compulsory fees — as a yearly percentage of the amount borrowed. Because it standardises everything into one figure, APR lets you compare loans with different rates, fees and terms on a like-for-like basis. By law, lenders must show the APR, which is why it's the figure to focus on rather than the headline interest rate alone.
Representative APR vs your APR
Advertised rates are usually a representative APR, which only has to be offered to 51% of accepted applicants. The other 49% can be charged more based on their credit profile. So the rate you actually get may be higher than advertised. Use lenders' soft-search eligibility checkers to see your personalised APR without harming your credit score.
How fees inflate the real cost
A loan with a low interest rate but a large arrangement fee can cost more than one with a slightly higher rate and no fee — and the APR captures this. The calculator above works backwards from your monthly payment and any fee to reveal the true APR, so you can see past marketing to the genuine cost of credit.
Compare total cost too
APR vs flat rate vs monthly rate
Beware quotes given as a "flat rate" — common in some car and point-of-sale finance. A flat rate charges interest on the original amount for the whole term, ignoring that you're paying it down, so the true APR is often roughly double the flat rate. Always insist on the APR. Credit cards quote a monthly rate too; multiply with care, as APR compounds.
Common mistakes
- Comparing interest rates, not APRs. Only APR includes compulsory fees. Two "5%" loans can cost very differently.
- Assuming you'll get the advertised rate. Representative APR goes to just 51% of applicants. Check your personalised rate.
- Falling for a flat rate. A flat rate hides a much higher true APR — often about double. Ask for the APR.
- Ignoring the total repayable. The clearest measure of cost is the total amount you'll pay back over the term.