Nominal vs Effective Annual Rate
ADS Team
Author
August 19, 2026
4 days ago
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In short: The nominal rate is the advertised annual rate before compounding. The effective annual rate accounts for compounding within the year, so a 6.5% nominal rate compounded monthly is an effective 6.70%. The gap widens as compounding gets more frequent and as the rate rises.
Key takeaways
- Effective rate = (1 + nominal/n)^n - 1, where n is compounding periods.
- At 6.5% compounded monthly the effective rate is 6.70%.
- The gap grows with the rate - at 15% it is over a full percentage point.
- Comparison rates use a standardised method and are not the same thing.
The formula and the gap
Effective annual rate = (1 + r/n)n − 1
| Nominal | Monthly compounding | Gap |
|---|---|---|
| 5.0% | 5.12% | 0.12 |
| 6.5% | 6.70% | 0.20 |
| 10.0% | 10.47% | 0.47 |
| 15.0% | 16.08% | 1.08 |
| 20.0% | 21.94% | 1.94 |
Where it matters most
On a mortgage the difference is modest but real. On credit cards and short-term lending it is substantial - a card advertising 19.99% has an effective annual rate near 21.9% if a balance is carried and interest compounds monthly.
It matters most when comparing products with different compounding frequencies, which is precisely where the advertised rate misleads.
Effective rate vs comparison rate
They answer different questions. The effective annual rate accounts for compounding. The comparison rate folds in fees using a standardised $150,000 / 25-year example. Neither captures the other, and neither includes everything.
Frequently asked questions
Which rate do lenders advertise?
The nominal annual rate, alongside the legally required comparison rate. The effective annual rate is rarely shown.
Does this change my repayment?
No. Your repayment is calculated using the monthly periodic rate. The effective rate is a way of comparing, not a separate charge.
Why does it matter for short-term lending?
Because fees expressed as a flat percentage over a short period annualise to very large numbers. A 1.5% fee over 45 days is over 12% annualised.
Related reading
- Comparison Rate: What It Includes and What It Hides
- Credit Cards: Interest-Free Periods and the Real Cost
- Invoice Finance and Debtor Finance: A Practical Guide
Sources
- Comparison rate guidance — ASIC Moneysmart
- National Consumer Credit Protection Regulations — Federal Register of Legislation
Information current as at 2 August 2026.
General advice warning: This article contains general information only. It does not take into account your objectives, financial situation or needs, and it is not personal credit or financial advice. Consider whether it is appropriate for you and seek advice from a licensed credit representative before acting.
Any interest rate shown is an example only and is not an offer of credit. Where a rate is quoted, the applicable comparison rate is available from the relevant lender and should be considered alongside it.
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