What Is the Difference Between AER and APR?

AER and APR are both ways of expressing financial rates on an annual basis, but they are designed for different purposes.

AER stands for Annual Equivalent Rate. It is mainly used with savings accounts and helps show the annual return while taking the effect of compounding into account.

APR stands for Annual Percentage Rate. It is mainly used with borrowing and provides an annual measure of the cost of credit, including interest and certain fees or charges.

This means the two percentages should not be treated as interchangeable. A 5% AER on a savings account and a 5% APR on a loan do not describe the same financial relationship simply because the percentages happen to be identical.

The useful rule is to compare like with like: AER with AER when comparing comparable savings products, and APR with APR when comparing comparable borrowing products.

If you want to understand the underlying percentage before looking at these annual measures, What Is Interest? explains how interest works more generally.

What Does AER Mean?

AER stands for Annual Equivalent Rate. It is mainly used with savings accounts to express the return from interest on a standard annual basis.

One reason this is useful is that savings accounts can calculate or credit interest at different intervals. One account might credit interest monthly, for example, while another might credit it annually.

Where credited interest remains in an interest-bearing account, it may itself contribute to later interest calculations. AER takes this compounding effect into account when expressing the equivalent annual rate.

This gives savers a more consistent percentage with which to compare accounts, rather than requiring them to work out how different interest-payment frequencies could affect the annual return.

A higher AER generally indicates a higher annual return when accounts are being compared on an equivalent basis. However, that does not mean the account with the highest AER is automatically the most appropriate account in every situation.

The wider terms still matter. An account could have withdrawal restrictions, balance requirements, an introductory or bonus rate, or an interest rate that can change.

Fixed vs Variable Interest Rates explains what it means when the underlying rate can change rather than remaining fixed for an agreed period.

Why Does AER Take Compounding Into Account?

Compounding matters because interest that has already been credited to a savings account may itself begin earning interest.

Suppose an account credits interest several times during a year. Once the first interest payment has been added to the interest-bearing balance, later calculations may be based on a slightly larger amount.

The saver is therefore potentially earning interest not only on the original savings but also on interest that has already been credited.

If another account credits interest at a different frequency, simply looking at the periodic rates could make the two accounts harder to compare.

AER provides an annual equivalent that takes the compounding effect into account, allowing savings rates to be presented on a more consistent basis.

This does not mean every savings account compounds in exactly the same way. The product terms determine how interest is calculated and when it is credited.

How Often Does Compound Interest Compound? explains why the timing of compounding can affect the result, while Simple Interest vs Compound Interest looks at the underlying difference between interest calculated only on an original amount and interest that can build on previous interest.

What Does APR Mean?

APR stands for Annual Percentage Rate. It is mainly used with borrowing and is designed to provide a standardised annual measure of the cost of credit.

The important distinction is that APR is not necessarily the same as the underlying interest rate.

A borrowing product can involve interest as well as certain compulsory fees or charges. APR can incorporate relevant costs alongside the interest rate so that borrowers have a more consistent annual percentage with which to compare credit products.

Suppose two loans have similar headline interest rates but one has an arrangement fee that forms part of the cost included in the APR calculation. The two loans could consequently display different APRs even though their underlying interest rates appear similar.

This is why APR can be more useful for comparing borrowing than looking at the headline interest rate alone.

However, APR should not be interpreted as an exact prediction of the number of pounds you will ultimately pay. The actual cost of borrowing can depend on the amount borrowed, the repayment period, your repayment schedule and the terms of the particular agreement.

Some costs may also fall outside the APR calculation. Charges that arise only in particular circumstances, for example, should not simply be assumed to be represented by the headline APR.

APR is therefore best understood as a standardised comparison measure, rather than a complete description of every possible cost associated with borrowing.

AER vs APR: What Is the Practical Difference?

Although AER and APR are both expressed as annual percentages, they answer fundamentally different questions.

This distinction also explains why a 5% AER should not be interpreted as financially equivalent to a 5% APR.

With AER, the percentage is helping describe the annual return from savings.

With APR, the percentage is helping describe the annual cost of borrowing.

The fact that both are percentages does not make them measurements of the same thing.

What Is Representative APR?

When borrowing is advertised in the UK, you may also encounter the term representative APR.

A representative APR does not necessarily mean every successful applicant will receive the advertised rate. For relevant credit advertising, the representative APR generally has to be the rate that at least 51% of customers entering into agreements as a result of the promotion are expected to receive or better.

That still leaves the possibility that other successful applicants will be offered a higher APR.

Suppose a personal loan is advertised at:

6.9% representative APR

That does not guarantee that an individual applicant will receive an APR of 6.9%. The rate actually offered can depend on the lender’s assessment and the terms available to that applicant.

The distinction is important because the word representative describes the advertised comparison rate rather than promising a particular rate to every customer.

This is another reason to distinguish between an advertised APR and the terms of an individual credit agreement. The APR actually offered to you is what matters for your own borrowing, rather than assuming you will necessarily receive the representative rate shown in an advert.

What Doesn’t AER or APR Tell You?

AER and APR make financial products easier to compare, but neither percentage tells you everything about a savings account or borrowing agreement.

What Else Should You Check?

AER and APR provide useful annual comparison measures, but the wider terms of the financial product can still affect how it works in practice.

Whether the rate can change

A savings or borrowing rate may be fixed for a period or variable. Knowing today’s percentage does not necessarily tell you what rate will apply in the future.

Access and repayment conditions

Savings accounts can restrict withdrawals, while borrowing agreements can have conditions governing repayments or early settlement.

Balance or borrowing amount

Savings products can have minimum or maximum balance conditions, while the amount borrowed can affect the overall borrowing cost and the terms available.

How long the product lasts

The savings term or borrowing period can affect the financial outcome even when the annual percentage appears similar.

Fees and other conditions

Product terms can contain fees, charges or conditions that should be considered alongside the headline annual percentage.

The rate actually available

An advertised representative APR may not be the APR offered to every successful borrower, while some savings rates may depend on particular account conditions being met.

The purpose of AER and APR is therefore not to reduce an entire financial product to one percentage.

Instead, they provide standardised annual measures that make one important part of the product easier to compare.

For savings, AER can help you compare the annual return before considering the wider account conditions.

For borrowing, APR can help you compare the annual cost of similar credit products before considering the amount borrowed, repayment structure and other relevant terms.

Understanding the Rate Behind the Percentage

AER and APR tell you how a rate is being presented for comparison, but there is another question underneath them: how does the interest itself become the amount you eventually earn or pay?

That depends on factors including the balance, applicable rate, time period and the way the financial product calculates or applies interest.

How Banks Calculate Interest explains this process in more detail, including the distinction between interest being calculated and interest actually being credited or charged.

Calfiny’s Interest Rate Calculator can also help you explore the mathematical relationship between a starting amount, final amount, timeframe and annual interest rate.

It should not be used to convert AER into APR or APR into AER. The two measures serve different purposes and there is no simple conversion that turns one into an equivalent version of the other.

Conclusion

AER and APR both express financial rates annually, but they are designed to answer different questions.

AER is mainly used with savings and expresses an annual return while taking compounding into account.

APR is mainly used with borrowing and provides an annual measure of the cost of credit, including interest and certain fees or charges.

The important principle is to compare like with like. When comparing comparable savings products, AER provides a useful annual measure of return. When comparing comparable borrowing products, APR provides a useful annual measure of cost.

Neither percentage tells you everything about the underlying product, so the wider terms and conditions still matter alongside the advertised rate.