CD Calculator
Estimate CD maturity value, APY-to-APR conversion, monthly interest, and early withdrawal penalty by withdrawal month.
Last reviewed: June 2026Quick Answer
A certificate of deposit (CD) earns a fixed interest rate for a set term. The final value uses compound interest: a $10,000 CD at 4.5% APY for 2 years grows to about $10,920. Enter your deposit, rate, and term above to see the maturity value and total interest earned. APY already accounts for compounding, so the math is straightforward.
Monthly Interest Breakdown
| Month | Opening Balance | Interest | Closing Balance |
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About the CD Calculator
This CD calculator estimates the maturity value of a certificate of deposit from the deposit amount, quoted APY, term length, compounding schedule, and early-withdrawal penalty. It is built around the way U.S. banks usually advertise CDs: APY is the headline yield because it already includes compounding, while the nominal rate needed for month-by-month math depends on the compounding frequency.
The calculator starts with the APY you enter, then derives the nominal APR for the selected compounding schedule with this formula: APR = n x ((1 + APY)^(1/n) - 1). Here, n is the number of compounding periods per year. The maturity value is then Deposit x (1 + APR / n)^(n x term years). Total interest is maturity value minus the deposit, and average monthly interest is the total interest divided by the term in months.
Early Withdrawal Penalty Model
The penalty section now uses the withdrawal month you enter instead of assuming the full maturity balance. It estimates the balance at that month, then subtracts deposit x APR / 12 x penalty months. For the default $10,000 deposit at 5.00% APY, monthly compounding, a 12-month term, and a three-month interest penalty at month six, the estimated withdrawal balance is about $10,246.95 and the net after penalty is about $10,124.73.
Actual banks can define penalties differently, and some CDs restrict early withdrawal or treat brokered CDs differently. Some institutions deduct a penalty from principal if the CD has not earned enough interest yet. That is why the calculator flags when the modeled penalty is larger than the interest earned by the selected withdrawal month.
How to Use the Result
Use the maturity value to compare quoted CDs with the same deposit and term. Use the APR and effective annual rate boxes to understand how compounding changes the math behind the APY. Use the monthly breakdown when you want to see interest accrual over time, especially for shorter terms where a one-year APY can make the return feel larger than the actual dollar interest.
This calculator does not evaluate taxes, inflation, account fees, renewal behavior, rate changes after maturity, laddering strategy, or deposit-insurance limits. For a real account, compare the bank's Truth in Savings disclosure, early-withdrawal language, maturity instructions, and FDIC or NCUA insurance status.
Sources and Further Reading
For penalty context, see the OCC-hosted HelpWithMyBank page on CD early withdrawal penalties. For rate-disclosure context, review the CFPB Regulation DD appendix on annual percentage yield calculations and the FDIC overview of insured deposit products.