How CD interest is calculated
Banks quote CDs by APY, which already includes compounding. To find the value at maturity, grow the deposit by the APY for the length of the term:
If you only know the stated interest rate and how often it compounds, convert it first:
Example
$10,000 in a 12-month CD at 4.25% APY is worth $10,425 at maturity — $425 of interest. If the CD were broken early with a typical three-month interest penalty, you’d give up about $105.
Things to check before opening a CD
- Early-withdrawal penalty: usually 3–12 months of interest depending on the term. No-penalty CDs exist but pay a little less.
- Insurance: CDs at FDIC banks and NCUA credit unions are insured up to $250,000 per depositor, per institution, per ownership category.
- Renewal: many CDs roll over automatically at maturity, often at a lower rate. Set a reminder for the grace period.
- Laddering: splitting money across 1-, 2-, 3-, 4- and 5-year CDs gives you a maturing CD every year while capturing longer-term rates.
Related Fixed-Income & Capital Preservation Tools
Certificates of Deposit provide guaranteed, FDIC-insured fixed returns. Convert stated interest rates to true yields with our APY Calculator, model long-term compounding growth via the Compound Interest Calculator, track liquid cash reserves using the Savings Calculator, and evaluate real purchasing power erosion with the Inflation Calculator.
Frequently asked questions
Is CD interest taxable?
Yes, as ordinary income in the year it's credited — even if you can't withdraw it until maturity. CDs inside an IRA are tax-deferred or tax-free.
Are CDs better than a high-yield savings account?
A CD locks in a rate, which helps if rates fall, but your money is tied up. High-yield savings is flexible but its rate can drop at any time. Many people use savings for emergencies and CDs for money with a known future date.
What happens if rates rise after I open a CD?
Your rate stays the same until maturity. Some banks offer bump-up CDs that let you raise the rate once, usually at a slightly lower starting rate.