APR vs AER vs EAR: what is the difference?

When banks and lenders quote interest, three similar acronyms appear again and again. APR, AER and EAR all try to make costs or returns comparable, yet each one does a slightly different job. Here is a clear guide so you can read a rate and know exactly what it means.

Quick definitions

• APR: Annual Percentage Rate. Used for borrowing such as credit cards and loans. It rolls the interest rate and most compulsory fees into a single yearly cost of credit, averaged across the term.

• AER: Annual Equivalent Rate. Used for savings accounts. It shows the yearly rate you would earn if interest were paid and compounded once a year, so different payment frequencies can be compared fairly.

• EAR: Effective Annual Rate. Used for overdrafts and some variable credit. It is an annualised rate that reflects intra-year compounding but excludes set fees. Think of it as “AER for borrowing” where fees are not bundled.

Why compounding matters

Compounding means you earn or pay interest on interest. If a bank pays 5 percent nominal per year but credits interest monthly, your true yearly return is a touch higher because each month’s interest starts earning its own interest. AER captures that uplift. For borrowing, EAR captures the same effect in reverse.

If compounding did not exist, a 1 percent monthly rate would be 12 percent per year. With compounding it becomes about 12.68 percent, because each month grows the balance that the next month uses.

Where each measure is used

• APR is the headline figure on credit cards, personal loans and hire purchase. It is designed for comparison across different products that may charge different fees. If two loans show 9.5 percent APR and 10.2 percent APR, the first is cheaper overall for the stated example.

• AER appears on savings products. Banks may credit interest monthly or annually. AER lets you compare them fairly. A monthly rate that compounds to 5.12 percent AER beats a flat 5.00 percent credited once a year.

• EAR is common on current account overdrafts. It reflects the interest charged on the overdrawn balance with compounding. Some providers also add daily or monthly fees, which are not included in EAR, so you must still check the small print.

Simple formulas

You do not need to memorise these, yet they help explain the logic.

• From a periodic rate r applied n times per year, the effective annual rate is

  \text{EAR} = (1 + r)^n – 1.

  For savings, this is your AER when no fees distort the picture.

• To estimate APR when there are no extra fees and the rate is fixed, APR aligns closely to EAR. Once fees, introductory rates or irregular repayments appear, lenders calculate APR using the true cash flows, which is why APR is the one to compare across loans.

Worked examples

Savings example

A bank offers 4.90 percent paid monthly. The monthly rate is roughly 0.408 percent. The effective yearly return is

(1 + 0.00408)^{12} – 1 \approx 5.02\%.

Advertised as 5.02 percent AER.

Overdraft example

An overdraft quotes 39.9 percent EAR. This already reflects compounding of the daily or monthly rate. If there is also a £2 monthly fee, the real cost will be higher than 39.9 percent once the fee is included. EAR does not include set fees.

Loan example

You borrow £5,000 for two years. Lender A charges a fixed 8.9 percent with a £99 arrangement fee. Lender B charges 9.2 percent with no fee. The APR calculation spreads the fee over the term and shows the overall yearly cost. Result: Lender A might show 10.1 percent APR, Lender B 9.2 percent APR, so B is cheaper despite the lower headline at A before the fee is considered.

Common pitfalls

• Mixing APR and AER. Never compare a loan’s APR with a savings AER. They answer different questions.

• Ignoring fees. APR includes most compulsory credit fees. EAR does not. Always scan for monthly account fees on overdrafts.

• Promotional rates. Introductory interest or bonus periods can make the early months look generous. APR smooths these for borrowing, AER typically assumes the on-going rate for savings.

• Payment frequency. For savings, monthly payers often beat annual payers at the same nominal rate because of compounding. AER reveals this.

Which one should I trust when choosing?

• Choosing a loan or credit card. Use APR for the headline comparison, then read the repayment schedule and any early settlement rules.

• Comparing overdrafts. Look at EAR to judge the interest cost, then factor in any fixed fees.

• Comparing savings. Use AER to rank accounts quickly. If you will move money in and out, also check withdrawal rules and bonus periods.

Convert between them in seconds

If you have a monthly rate and want the annual equivalent, or you need to turn a quoted AER into a monthly figure for planning, use our fast APR ↔ AER converter. It handles common compounding patterns and keeps the maths tidy so you can sense-check any offer. Try it here: https://stablenumbers.com/finance/apr-aer-converter.php

Clear terms, accurate sums and fewer surprises. Once you recognise what APR, AER and EAR each represent, you can compare like with like and make a decision that actually suits your pocket.