About the CD Calculator
A certificate of deposit trades flexibility for a guaranteed, fixed rate of return - you lock your money away for a set term in exchange for a higher, predictable rate than a typical savings account. Our CD Calculator shows exactly what your deposit will be worth at maturity.
How It Works
The calculator applies compound interest to your deposit at your CD's APY, using your chosen compounding frequency over the term length you enter (converted from months to years internally). The result is the exact maturity value and the interest earned above your original deposit.
Formula & Methodology
A CD's rate is locked at opening, which is what makes this a pure, single-scenario compound interest calculation rather than a projection with uncertainty - the math is the same lump-sum compounding formula used elsewhere, but because the rate can't change during the term, the result here is an exact figure rather than an estimate, assuming the deposit stays untouched to maturity.
Step-by-Step: Calculating It By Hand
- 1Convert the CD's term from months to years if needed.
- 2Divide the APY by the number of compounding periods per year to find the periodic rate.
- 3Raise (1 + periodic rate) to the power of total compounding periods over the term.
- 4Multiply by the deposit amount to find the maturity value, then subtract the deposit to isolate interest earned.
Examples
1-year CD
$10,000 at a 4.5% APY over 12 months with monthly compounding matures to roughly $10,459 - a fixed, predictable outcome regardless of what happens to market rates during the term.
Longer term
The same deposit in a 5-year CD at a similar rate compounds for much longer, though funds are locked up far longer and early withdrawal typically means a penalty.
Advantages
- Gives an exact maturity value for comparing CD offers from different banks
- Accounts for compounding frequency, which affects the final return slightly
- Useful for comparing a CD against a high-yield savings account with a similar rate
- Makes the fixed, predictable nature of CD returns concrete with real numbers
Common Mistakes
- Not accounting for early withdrawal penalties, which can erase months of earned interest
- Locking a large sum into a long-term CD right before rates rise, missing out on better rates elsewhere
- Comparing a CD's APY directly to a savings account's APY without checking compounding frequency differences
- Forgetting interest earned on a CD is taxable income in the year it's earned (or paid), even if you don't withdraw it
Edge Cases to Watch For
- Early withdrawal penalties (commonly a few months' worth of interest) apply if funds are accessed before maturity, which this maturity-value calculation doesn't factor in.
- APY already accounts for compounding frequency, while a stated 'interest rate' on some CDs might not - check which figure is being quoted before comparing offers.
- CD interest is taxable income in the year it's earned or credited, even though it isn't accessible until maturity for longer-term CDs.
- A callable CD can be redeemed by the issuing bank before maturity under certain conditions, which isn't reflected in this straightforward maturity projection.
Common Use Cases
- Comparing maturity values across CD offers from different banks
- Deciding between a CD and a high-yield savings account for a specific goal
- Planning around a CD's maturity date for a known future expense
- Laddering CDs of different terms for a mix of access and yield