Nominal rate versus APY
The nominal rate is the headline number a bank quotes, but it is not what you actually earn. Because interest is added several times a year and then starts earning interest itself, the real return is a little higher. That real return is the APY, or annual percentage yield. This calculator turns any nominal rate and compounding frequency into the APY, so you can see what a rate is genuinely worth.
The gap between the two comes entirely from how often interest compounds. At yearly compounding the nominal rate and the APY are the same. Move to monthly or daily and the APY creeps above the nominal rate, because each addition of interest gets a head start on earning more.
Two examples
A 12% nominal rate compounded monthly works out to an APY of about 12.68%. That extra 0.68% is the compounding you would miss if you compared on the nominal rate alone.
Take a savings account at 4% compounded daily. Its APY is about 4.08%, slightly ahead of a rival paying 4% compounded yearly at 4.00%. Same headline rate, different real return, and APY is what tells them apart.
How to use it
- Always compare savings accounts APY to APY, never nominal to nominal.
- On loans, do the reverse check: a low nominal rate can hide a higher effective cost once compounding is included.
- Remember frequency is the whole story here. If two products match on rate, the one that compounds more often wins.
What is the mistake to avoid?
Comparing a nominal rate on one product against an APY on another. Banks often advertise savings in APY (which looks bigger) and loans in nominal terms (which looks smaller). Convert everything to the same basis before you decide, or you are comparing two different things.
Frequently asked questions
Does a higher APY always mean more money?
For savings, yes, all else equal. Just make sure you are comparing APY to APY and checking any account fees or conditions.
How do I convert APY back to a nominal rate?
For the same compounding frequency, a higher APY always means a higher nominal rate. Compare like frequencies and the ranking stays the same.
Is APY the same as APR?
Not exactly. APR is usually the nominal rate; APY includes the effect of compounding, so APY is higher for the same nominal rate.
Why does frequency change APY?
More frequent compounding means interest is added and starts earning sooner, which raises the effective yield.
Which should I compare?
Compare APY to APY. It reflects the true annual cost or return once compounding is included.