CD interest compounds based on the frequency stated in the product terms. Most CDs compound daily or monthly. The standard formula is compound interest applied for the number of compounding periods in the term. If you want to compare how long your CD balance will fund withdrawals after maturity, use the Savings Duration Calculator.
Final Balance = P × (1 + r/n)^(n × t)
P = principal, r = annual rate (decimal), n = compounds/year, t = years
$10,000 at 5.0% APY, 12 months, monthly: $10,511.62
Calculate CD Interest Rate: APY vs APR Explained
APR and APY are not the same number. When comparing CDs, always use APY. The Truth in Savings Act requires banks to disclose APY on CDs so you can compare products accurately. The table below shows how much APY diverges from APR depending on compounding frequency at a 5% nominal rate.
Compounding
APR
Effective APY
$10K Earns
Annually
5.000%
5.000%
$500.00
Semi-annually
5.000%
5.063%
$506.25
Quarterly
5.000%
5.095%
$509.45
Monthly
5.000%
5.116%
$511.62
Daily
5.000%
5.127%
$512.68
The difference between annual and daily compounding at 5% is only $12.68 on a $10,000 deposit over 12 months. The rate itself matters far more than the compounding frequency for short-term CDs.
How to Calculate CD Interest Rate Per Month
Monthly CD interest is calculated by applying the monthly periodic rate to the current balance. Because interest compounds, each month earns slightly more than the previous. If you plan to reinvest CD earnings into a dividend reinvestment strategy, compare growth rates with the Dividend DRIP Calculator.
CD Interest Rate by Term: 3-Month, 6-Month, and 12-Month
Earnings depend heavily on your term. Rates and earnings shown below assume a $10,000 deposit at representative 2026 high-yield online bank rates, compounding monthly. Use the calculator above to enter your exact rate. For how CD savings fit into a retirement plan, the Roth IRA Contribution Calculator shows how much you can contribute alongside a CD strategy.
CD Term
Typical APY (2026)
Interest on $10K
Maturity Balance
3 months
4.50-5.20%
$112-$129
$10,112-$10,129
6 months
4.80-5.50%
$237-$270
$10,237-$10,270
12 months
4.50-5.30%
$450-$530
$10,450-$10,530
18 months
4.00-4.80%
$617-$743
$10,617-$10,743
24 months
3.80-4.50%
$776-$921
$10,776-$10,921
36 months
3.50-4.20%
$1,093-$1,319
$11,093-$11,319
60 months
3.20-4.00%
$1,730-$2,167
$11,730-$12,167
Rates reflect online bank high-yield CD ranges as of 2026. Rates change frequently. Verify with the issuing bank before opening.
Example Calculation
You deposit $10,000 in a 12-month CD at 5.0% APY, compounding monthly.
Principal: $10,000
Monthly rate: 5.0% / 12 = 0.4167%
Balance: $10,000 × (1.004167)^12
Maturity value: $10,511.62 (+$511.62 interest)
Common CD Interest Rate Mistakes
Comparing APR instead of APY across institutions
APY accounts for compounding frequency and is the correct metric for comparing CDs. A CD that compounds daily will produce a higher APY than one compounding monthly at the same stated APR. Always compare APY, not APR, when shopping rates.
Not modeling early withdrawal penalties before committing
Most CDs charge a penalty for early withdrawal, typically equal to 3 to 6 months of interest. A 12-month CD with a 6-month penalty can underperform a 6-month CD if you need access to your funds early. Run the penalty scenario before choosing term length.
Ignoring FDIC and NCUA insurance limits
Deposit insurance covers $250,000 per depositor per institution per ownership category. If you hold more than this at one bank, the excess is uninsured. Spreading large CD balances across multiple insured institutions eliminates this risk.
Laddering without accounting for reinvestment rate risk
CD laddering reduces interest rate risk by spreading maturities, but rolling over maturing CDs into a rate environment that has fallen locks in lower returns for the next period. Consider locking longer terms when rates are at cyclical highs.
Using the stated interest rate instead of APY for total interest calculations
If you enter the stated nominal rate instead of the APY into a CD calculator, you will underestimate the actual return on monthly or daily compounding CDs. Confirm which figure the institution is quoting before running calculations.
Consumer Financial Protection Bureau: consumer guide to CD terms, compounding, and deposit insurance rules
HR
Hassaan Rasheed
Developer and Researcher, CalculatorFlux
Researches and verifies the formulas, methodology, and source data behind each calculator on CalculatorFlux. All tools are built and checked against the cited references before publication.
Last updated: June 2026
Frequently Asked Questions
CD interest uses the compound interest formula: Final Balance = P x (1 + r/n)^(n x t). For a $10,000 CD at 5% APY compounding monthly for 12 months: $10,000 x (1 + 0.05/12)^12 = $10,511.62. That is $511.62 in interest earned. The calculator above does this instantly for any deposit, rate, and term you enter.
Online bank rates as of 2026. Rates change frequently.
Pro Tip
Short-term CDs (6 to 12 months) often pay more than long-term CDs in an inverted yield curve environment. Check rates across all terms before committing, especially when the Fed is cutting rates. Locking in a longer term may pay off more than chasing the highest short-term rate.