A certificate of deposit (CD) pays a fixed rate if you leave the money alone for a set term. This calculator shows exactly what you will have at the end: enter the deposit, the rate and the term in months, and it returns the interest earned and the value at maturity.
It also handles the questions that usually come up next. If your bank quotes a stated rate and a compounding schedule instead of an APY, switch the rate type and the tool converts it. If you might need the money early, enter the penalty from your agreement and see what you would actually walk away with. And if you want some of your cash to come due every year, the ladder planner splits your deposit into equal CDs with staggered maturity dates and totals the interest.
Reviewed by: CalcMojo Editorial Team
How CD interest is calculated
Banks quote CD rates as an annual percentage yield (APY). APY is the rate that already includes compounding, so it tells you the total growth over one year. For a CD held for a whole number of years, the maturity value is simply:
Value = Deposit x (1 + APY) ^ years
For terms that are not whole years, the exponent is months / 12. A $10,000 deposit at a 4.5% APY for 12 months earns $450 and becomes $10,450. For 24 months it becomes 10,000 x 1.045^2 = $10,920.25, so the interest is $920.25. For six months the interest is 10,000 x (1.045^0.5 - 1) = $222.52, which is a little less than half of $450 because the second half of a year earns interest on the first half's interest.
APY and Regulation DD
Federal rules require banks to quote APY on deposit accounts in a standard way so that offers can be compared. Regulation DD, which implements the Truth in Savings Act, defines APY for an account with a stated maturity as:
APY = 100 x [ (1 + Interest / Principal) ^ (365 / Days in term) - 1 ]
This calculator uses that relationship in reverse: Interest = Principal x ((1 + APY) ^ (days / 365) - 1). Regulation DD allows a 365-day or 366-day basis in a leap year, and your bank counts actual days, so a statement can differ from this tool by a few cents. Regulation DD also requires banks to disclose early-withdrawal penalties on time accounts, so look for that disclosure before you open one.
Converting APR to APY
Some banks, credit unions and online listings show a stated rate, often called the APR or nominal rate, together with a compounding frequency. To compare with an APY, convert:
APY = (1 + APR / n) ^ n - 1, where n is the number of compounding periods per year.
Going the other way: APR = n x ((1 + APY) ^ (1/n) - 1).
At a 5% stated rate, the APY is:
| Compounding | APY |
|---|---|
| Annually (n = 1) | 5.0000% |
| Semiannually (n = 2) | 5.0625% |
| Quarterly (n = 4) | 5.0945% |
| Monthly (n = 12) | 5.1162% |
| Daily (n = 365) | 5.1267% |
| Continuously | 5.1271% |
More frequent compounding adds only a small amount, which is why the APY is the number to compare. A 4.5% APY equals a stated rate of about 4.41% compounded monthly or 4.40% compounded daily. Choose "Stated rate / APR" in the calculator, pick the compounding, and it works out the APY for you and uses it for all results.
Early-withdrawal penalties
Cash out a CD before maturity and the bank normally charges a penalty, usually expressed as a number of months of interest. The amount and the length of term it applies to vary by bank, so use the figure in your own agreement. The calculator treats the penalty as the interest the CD would have earned over that many months, taken from the first months of the CD.
Example with $10,000 at 4.5% APY and a three-month penalty: the penalty is 10,000 x (1.045^0.25 - 1) = $110.65. If you cash out after six months, you have earned $222.52, the penalty takes $110.65, and you receive about $10,111.87. That is $338 less than holding to the 12-month maturity.
Cash out too early and the penalty can be larger than the interest you have earned. After two months in the same example you have earned about $73 and the penalty is still $110.65, so you get back less than you deposited. The calculator flags this case. Whether to break a CD depends on the penalty and on what you could earn elsewhere, so run the numbers before you withdraw.
Building a CD ladder
A CD ladder divides your money into several CDs with different terms, for example one-, two-, three-, four- and five-year CDs, each holding an equal share. When the one-year CD matures you can spend the cash or reinvest it in a new five-year CD, which keeps the ladder going. Over time you hold longer-term rates but still have a CD maturing every year.
The ladder planner takes your deposit and a number of rungs, then spaces the terms evenly (every 12 months by default). Each rung gets its own APY box, since longer terms often pay different rates. For $100,000 in five rungs of $20,000, with every rung at 4.5% APY, the interest at maturity is:
| Rung | Term | Interest |
|---|---|---|
| 1 | 12 months | $900.00 |
| 2 | 24 months | $1,840.50 |
| 3 | 36 months | $2,823.32 |
| 4 | 48 months | $3,850.37 |
| 5 | 60 months | $4,923.64 |
The total is $14,337.83. Because each rung matures at a different time, the total is paid out over five years and not all at once.
A ladder trades a bit of potential yield for flexibility. If rates rise, maturing rungs can be renewed at the new rates. If rates fall, you still hold the older, higher-rate rungs. It also limits how much money is exposed to a single early-withdrawal penalty.
Deposit insurance limits
CDs at FDIC-insured banks are covered by deposit insurance. The standard insurance amount is $250,000 per depositor, per insured bank, per ownership category. CDs at the same bank count together with your savings and checking accounts in the same ownership category, so a ladder built at one bank does not multiply your coverage. If your total in a category at one bank would pass $250,000, consider spreading the money across banks, or look at the FDIC's rules for joint accounts and other ownership categories. Credit unions that are federally insured by the NCUA offer share certificates covered by the same standard amount.
The calculator shows a notice when your deposit is above $250,000.
What the calculator does not do
It does not subtract taxes. Interest on a CD is generally taxable income in the year it is credited, even if you do not withdraw it, so your after-tax return will be lower. It does not model CDs that pay interest out monthly instead of compounding, variable-rate CDs, bump-up CDs, or a bank's specific day-count conventions. Inflation also matters: compare your APY with the inflation rate to see your real return, which our inflation calculator can help with.
Frequently asked questions
How much interest will a $10,000 CD earn?
At an illustrative 4.5% APY, $10,000 earns $450 over 12 months and $920.25 over 24 months. Use your own APY and term in the calculator to see your result.
What is the difference between APR and APY on a CD?
APR is the stated annual rate before compounding. APY includes the effect of compounding within the year, so it is slightly higher when interest compounds more than once a year. Banks must quote APY so that CD offers can be compared, and it is the better number to use.
How is an early-withdrawal penalty calculated?
Most banks charge a set number of months of interest, and the number is longer for longer terms. This calculator takes the interest the CD would earn over those months at its APY. Your bank's method may differ slightly, so use the disclosure in your agreement.
Can I lose money by withdrawing a CD early?
Yes. If the penalty is larger than the interest you have earned so far, the bank may take the difference from your principal. The calculator shows this when it happens.
Are CDs insured?
CDs at FDIC-insured banks are insured up to the standard amount of $250,000 per depositor, per insured bank, per ownership category. Balances in the same category at the same bank are added together.
What is a CD ladder?
A CD ladder splits your money across CDs with staggered maturity dates, such as one to five years. As each one matures you can reinvest or use the cash, which gives you regular access and lets you capture new rates.
Does the calculator include taxes?
No. CD interest is generally taxable as ordinary income, so your after-tax return will be lower than shown.
Sources & Methodology
- FDIC: Understanding Deposit Insurance — standard insurance amount of $250,000 per depositor, per insured bank, per ownership category.
- CFPB: Regulation DD (12 CFR Part 1030), Appendix A — the APY formula for accounts with a stated maturity: APY = 100[(1 + Interest/Principal)^(365/Days in term) - 1], and the 365- or 366-day basis for leap years.
- CFPB: Regulation DD overview — Regulation DD, implementing the Truth in Savings Act, requires APY disclosure for deposit accounts.
- APR-to-APY conversion uses the standard compound-interest relationship APY = (1 + APR/n)^n - 1. Early-withdrawal penalties vary by bank and are not set by a federal rate, so the penalty length is an input you control; the way the calculator turns it into dollars is our assumption.
- The 4.5% default rate is illustrative and is not a current market rate.
This calculator provides estimates for educational purposes only. It is not financial advice. Results depend on the rate, compounding and penalty terms you enter and may differ from your bank's figures. The default rate is illustrative, not a current market rate. Check your CD agreement, and consult a qualified financial professional before making decisions.
Data accurate as of: November 2026