What is a certificate of deposit?
A CD is a deposit account with a defined term. The institution pays interest under its disclosure while the money remains on deposit, and the account reaches maturity at the end of that term. Traditional CDs usually restrict withdrawals before maturity and can charge an early-withdrawal penalty. Unlike an investment return, a stated deposit yield follows account terms rather than daily market prices.
Before comparing two CDs, line up the APY, term, minimum opening amount, balance tier, quote date, early-withdrawal penalty, grace period, renewal instructions, and any promotional conditions. A higher maturity balance can simply reflect a longer lockup or larger deposit; it does not by itself identify the more flexible product.
How CD interest is calculated
The calculator models one opening deposit and leaves every dollar of interest in the CD until maturity. It does not add later deposits or remove periodic interest payments.
- Use the formula that matches the quoted rate
With APY, maturity balance is P × (1 + APY)^t. With a nominal annual rate r compounded n times per year, it is P × (1 + r/n)^(n×t). In either case, interest earned equals maturity balance minus the opening deposit. The APY calculator can convert a nominal rate and frequency before two deposit disclosures are compared.
- Check the $10,000 example
At a 5% annual rate compounded annually for three years, $10,000 grows to $11,576.25. The annual interest is $500.00 in year one, $525.00 in year two, and $551.25 in year three because prior interest remains in the balance. Total gross interest is $1,576.25.
- Treat the schedule as an estimate
The page keeps full precision during the calculation and rounds displayed money to cents. An institution can use specific calendar dates, actual-day conventions, crediting intervals, or rounding rules, so its official maturity illustration can differ slightly from a term expressed only in months or years.
APY vs. nominal interest rate
The two rate inputs describe related but different quantities. Choosing the right mode prevents compounding from being counted twice or omitted.
APY already includes compounding
Annual percentage yield expresses the effective one-year growth when interest stays on deposit. If the disclosure gives APY, enter that APY directly. A separate daily, monthly, or quarterly selector must not change an APY-based result because the frequency effect is already built into the yield.
A nominal rate needs its frequency
A nominal annual interest rate states the yearly rate before within-year compounding. Monthly compounding divides that rate across 12 periods; daily compounding uses 365 modeled periods. The resulting effective APY can be slightly higher than the nominal rate when the stated rate is positive.
APR is not the usual CD comparison yield
APR commonly annualizes borrowing costs, while United States deposit disclosures compare interest-bearing accounts with APY. If a CD source uses APR or another annual-rate label, verify whether it means a nominal deposit rate and find the stated compounding frequency before entering it as an interest rate.
Before choosing a CD term
Projected interest matters only alongside the rules for accessing and moving the deposit. Review the current account disclosure for every item below.
- Early withdrawal: note the penalty formula, whether principal can be reduced, and whether partial withdrawals are allowed. This calculator assumes the CD is held to maturity and subtracts no penalty.
- Maturity and renewal: check the maturity date, grace period, automatic-renewal setting, and method for changing instructions. Today's rate is not a forecast of the renewal APY.
- Minimums and tiers: confirm the opening minimum and the balance range that earns the quoted yield. A conditional promotional rate is not equivalent to an unconditional APY.
- Taxes and purchasing power: displayed interest is gross. Tax timing, withholding, inflation, fees, and individual after-tax outcomes are outside this calculation.
CD ladders and common CD types
A CD ladder divides money among separate maturity dates—for example, one-, two-, and three-year CDs—instead of placing the whole amount in one term. As each rung matures, its balance can be used or placed into a new term. A ladder can create more frequent access, but every rung needs its own principal, APY, maturity date, and penalty review. Future renewal rates remain unknown.
Traditional fixed-rate CDs are the simplest modeled fit. Bump-up or step-up CDs can change rates under defined rules; no-penalty or liquid CDs alter early-access terms; callable CDs can be ended by the issuer; brokered CDs can add intermediary, ownership, and secondary-market considerations. These features are not captured by one fixed-rate maturity formula. For Treasury savings bonds instead of bank deposits, use the Treasury savings bond calculator guide. For a household cash-flow check before locking funds, use the living expenses calculator.
FDIC and NCUA deposit insurance
Qualifying CDs at an FDIC-insured bank are deposit products, but coverage depends on the depositor, insured institution, ownership category, and aggregate balances—not simply the number of account names. Federally insured credit unions use NCUA share insurance under their own coverage framework. Confirm the actual insured institution and ownership structure with official tools and records.
This calculator does not verify insurance, membership, account ownership, brokered-deposit placement, or whether a product sold by a bank is itself an insured deposit. It also does not fetch current rates, interpret a contract, calculate tax, or decide whether a term suits a particular person. The institution's dated disclosure controls when it differs from this educational estimate.