About the CD Calculator
This CD calculator shows how much a certificate of deposit will be worth when it matures. Enter the amount you plan to deposit, the rate the bank quotes, the term in months and how often interest compounds, and you get the maturity value, the total interest, the average interest per month and the interest left after tax.
Banks usually advertise CDs by APY, which already includes compounding, but some quote the underlying interest rate instead. Choose which one you were given and the calculator converts between them, so you can compare a 6-month, 12-month or 5-year CD from different banks on equal terms.
It assumes you leave the principal and interest untouched until maturity and that the rate is fixed for the whole term, which is how standard CDs work. Withdrawing early usually triggers a penalty of several months of interest, which is not included here.
With the default inputs, the value at maturity is $26,125.00. Change any value above to recalculate instantly.
How to use the cd calculator
- 1Enter how much you will deposit in the CD.
- 2Enter the rate and choose whether the bank quoted it as APY or as an interest rate.
- 3Set the term in months (e.g. 6, 12, 18, 60).
- 4Pick the compounding frequency from the account disclosure.
- 5Optionally add your tax rate to see the interest you actually keep.
Formula and method
A CD grows by compound interest on a fixed rate. If you enter an APY, the maturity value is simply the deposit multiplied by (1 + APY) raised to the number of years in the term (months ÷ 12) — compounding is already built into the APY. If you enter the interest rate instead, it is first converted to APY using the compounding frequency.
Interest earned is maturity value minus deposit. After-tax interest multiplies interest by (1 − tax rate), because CD interest is taxed as ordinary income in the year it is credited. The APR shown is the nominal rate that produces the APY under the chosen compounding.
- A
- Value at maturity
- P
- Amount deposited
- APY
- Annual percentage yield as a decimal
- r
- Nominal annual interest rate (APR) as a decimal
- n
- Compounding periods per year
- m
- Term in months
Worked examples
$25,000 in a 12-month CD at 4.5% APY
Because the rate is an APY, one year of growth is exactly 4.5%: $25,000 × 1.045 = $26,125, or $1,125 of interest (about $93.75 a month). With monthly compounding that APY corresponds to a 4.41% nominal rate.
5-year CD, 4% rate compounded daily
Daily compounding turns a 4% rate into a 4.081% APY. Over five years $10,000 grows to about $12,213.89, earning $2,213.89 — more than 5 × $400 because each year’s interest earns interest too.
18-month CD, 5% compounded quarterly, 22% tax
Six quarters at 1.25% each grow $50,000 to $53,869.16, earning $3,869.16. In the 22% bracket, about $851 goes to tax, leaving $3,017.94 of interest.
Frequently asked questions
What happens if I withdraw money from a CD early?+
Most banks charge an early withdrawal penalty, commonly 3 to 12 months of interest depending on the term. On a short CD the penalty can eat into principal, so only lock up money you will not need before maturity.
Is CD interest taxable?+
Yes. In the US, CD interest is taxed as ordinary income in the year it is credited to your account, even if the CD has not matured. Your bank reports it on Form 1099-INT when it totals $10 or more for the year.
Are CDs FDIC insured?+
CDs at FDIC-member banks are insured up to $250,000 per depositor, per bank, per ownership category. Credit union share certificates have the same coverage through the NCUA.
What is the difference between the CD rate and APY?+
The interest rate is the nominal rate before compounding; APY includes compounding and shows what you earn in a year. A 4.40% rate compounded monthly equals roughly 4.49% APY. Compare CDs using APY.
What happens when a CD matures?+
You get a grace period, often 7 to 10 days, to withdraw or move the money. If you do nothing, many banks automatically renew it for the same term at the current rate, which may be lower.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.