CD Calculator
A CD calculator estimates how much a certificate of deposit (CD) will be worth at maturity based on your deposit amount, annual percentage yield (APY), term length, and compounding frequency. Banks and credit unions sell CDs as fixed-term, fixed-rate savings products: you lock in a set amount of money for a specific number of months in exchange for a guaranteed rate that usually runs higher than a standard savings account. Enter your starting deposit, the APY your institution quotes, the term in months, and how often interest compounds (monthly, quarterly, or annually), and this calculator projects your ending balance and total interest earned. Because a CD's rate and term are fixed once you open the account, the projection assumes the quoted APY holds steady for the full term with no additional deposits, no withdrawals, and no early closure.
Quick answer
CD growth depends on three inputs you control: your deposit amount, the APY, and the term length.
What this tells you
- •CD growth depends on three inputs you control: your deposit amount, the APY, and the term length.
- •Compounding frequency (monthly, quarterly, or annually) changes the ending balance slightly because interest earns interest more often as frequency increases.
- •This calculator projects the estimated ending balance and total interest earned at the end of your chosen term.
- •Results assume the APY stays fixed for the entire term with no additional deposits or partial withdrawals.
- •The estimate does not include taxes on interest income, account fees, or early withdrawal penalties.
- •A longer term or a higher APY generally increases projected earnings, but it also locks your funds in for longer.
How to Use
- 1Enter your starting deposit amount, the sum you plan to put into the CD when you open it.
- 2Enter the APY (annual percentage yield) your bank or credit union is quoting for that specific CD product.
- 3Enter the term length in months, for example 12 for a one-year CD or 60 for a five-year CD.
- 4Select the compounding frequency (monthly, quarterly, or annually). Check your CD's disclosure statement if you are not sure which one applies.
- 5Select Calculate to view your estimated maturity balance, total interest earned, and the term expressed in years.
How It Works
Formula
Ending balance = Deposit x (1 + APY/n)^(n x t)The calculator converts your APY into a periodic rate by dividing it by the number of compounding periods per year (n), then applies that rate once for every period across your term. Using P for your deposit, r for the decimal APY, n for compounds per year, and t for the term in years, ending balance equals P x (1 + r/n) raised to the power of (n x t). The number of periods (n x t) is rounded to the nearest whole period before the calculation runs, and interest earned is simply the ending balance minus your original deposit. All dollar figures are rounded to the nearest cent to match how a bank would report your balance.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
$10,000 CD, 4.8% APY, 2-year term, monthly compounding
With monthly compounding, the periodic rate is 4.8% ÷ 12 = 0.4% per month, applied across 24 periods (2 years x 12). Ending balance = $10,000 x (1.004)^24 = $11,005.48, which works out to $1,005.48 in total interest over the two-year term.
$5,000 CD, 5.25% APY, 1-year term, quarterly compounding
Quarterly compounding applies a periodic rate of 5.25% ÷ 4 = 1.3125% four times over the one-year term. Ending balance = $5,000 x (1.013125)^4 = $5,267.71, or $267.71 in interest for the year.
$25,000 CD, 4.5% APY, 5-year term, annual compounding
Annual compounding applies the full 4.5% rate once per year across 5 periods. Ending balance = $25,000 x (1.045)^5 = $31,154.55, which is $6,154.55 in interest earned over the five-year term.
$2,000 CD, 3.75% APY, 6-month term, monthly compounding
For a short six-month CD, the periodic rate is 3.75% ÷ 12 = 0.3125% per month, applied across 6 periods (0.5 years x 12). Ending balance = $2,000 x (1.003125)^6 = $2,037.79, or $37.79 in interest for the half-year term.
$50,000 CD, 5.0% APY, 3-year term, quarterly compounding
With quarterly compounding, the periodic rate is 5.0% ÷ 4 = 1.25%, applied over 12 quarters across the three-year term. Ending balance = $50,000 x (1.0125)^12 = $58,037.73, for $8,037.73 in total interest.
$1,000 CD, 4.0% APY, 9-month term, monthly compounding
A nine-month term rounds to 9 monthly periods (0.75 years x 12). Ending balance = $1,000 x (1 + 0.04/12)^9 = $1,030.40, or $30.40 in interest for the term.
Common mistakes
- Confusing APY with APR. APY already accounts for compounding, while APR does not, so comparing a CD's APY directly to a loan's APR understates the CD's real return.
- Ignoring early withdrawal penalties. Most CDs charge a penalty, often calculated as a set number of months' interest, if you withdraw before maturity, and that penalty can offset or exceed the interest you have earned so far.
- Assuming the CD renews at the same rate. When a CD matures, many banks automatically renew it into a new CD at whatever rate is current then, which can be lower than your original rate.
- Overlooking the deposit insurance limit. FDIC and NCUA coverage is typically capped at $250,000 per depositor, per institution, per ownership category, so very large deposits may need to be split across institutions.
- Forgetting that CD interest is usually taxable in the year it is credited, even if you do not withdraw the funds before maturity.
- Comparing CDs by headline rate alone. Two CDs with the same quoted APY can produce different real-world outcomes once minimum deposit requirements, compounding frequency, and penalty terms are factored in.
Limitations
This calculator projects a fixed APY compounding steadily for the exact term you enter. It does not account for taxes on interest income, early withdrawal penalties, account fees, minimum balance requirements, or the possibility that your bank changes its CD terms before maturity. Actual maturity value can differ from this estimate if any of those factors apply to your specific account.
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