CD / APY Calculator

Calculate a CD at maturity

Enter a deposit, rate and term to estimate the value at maturity and interest earned. If the rate is quoted as APY, use it directly. If it is a nominal APR, switch rate type and choose how often interest compounds; the calculator converts it to effective APY first.

The result also shows the return over the chosen term. That is different from APY when the CD lasts less or more than one year.

APY versus nominal APR

Annual percentage yield is the effective annual growth after compounding. A deposit earning 5% APY becomes 5% larger after one year under the assumptions behind the disclosed yield.

A nominal annual rate does not include the effect of interest being added during the year. Its APY is:

APY = (1 + nominal rate ÷ periods)periods − 1

At a 12% nominal rate compounded monthly, the effective APY is about 12.683%, not 12%. More frequent compounding increases APY, but the difference becomes progressively smaller.

Terms shorter than a year

APY remains an annual comparison rate even when the CD term is three, six or nine months. The calculator values a partial year with:

maturity value = deposit × (1 + APY)months/12

A six-month return is therefore lower than the quoted APY. That does not mean the APY is wrong; it means the money was deposited for less than a year.

Interest stays in the account

The estimate assumes interest remains on deposit and compounds until maturity. Withdrawing interest as it is paid reduces the maturity value because that interest no longer earns additional interest.

The FDIC’s Truth in Savings examination guidance notes that APY disclosures can assume interest remains until maturity and that withdrawals reduce earnings where applicable. The actual product disclosure determines the calculation and payment schedule.

Early withdrawal and renewal

CDs commonly restrict access for a fixed term. An early withdrawal can forfeit a stated amount of interest or trigger another penalty, and formulas differ across products. No generic calculator can infer that penalty from APY alone, so this one assumes the deposit is held to maturity.

At maturity, an institution may pay the balance out or renew the CD after a grace period. A renewal can use a new rate. This calculation stops at the entered term and does not assume that today’s rate continues.

What the estimate excludes

Tax, fees, minimum-balance rules, bonuses and early-withdrawal penalties are not included. Deposit-insurance eligibility and limits depend on the institution, ownership category and jurisdiction; the calculator makes no claim about them.

Use the institution’s account disclosure for the binding rate and terms. This page is comparison arithmetic, not a deposit recommendation or financial advice.

Frequently asked questions

How is CD interest calculated from APY?

APY is treated as a full year's effective growth. For a term in months, the balance is multiplied by one plus APY raised to months divided by 12.

What is the difference between APR and APY?

A nominal APR states the annual rate before within-year compounding. APY states the effective annual yield after compounding, making deposit products easier to compare.

How does compounding frequency change APY?

At the same nominal APR, more frequent compounding produces a slightly higher APY because interest is added to the balance sooner and begins earning interest itself.

Why is a six-month return lower than the APY?

APY is annualized. A six-month CD is held for only half a year, so its return over that term is lower even though the comparison rate is quoted per year.

Does the calculator include an early-withdrawal penalty?

No. Penalty formulas vary by institution and product. The estimate assumes the deposit remains in the CD until maturity.

What happens when a CD matures?

The institution's agreement controls. A CD may pay out, enter a grace period, or renew automatically at the rate then available. The calculator stops at the entered maturity and does not assume renewal.

Are CD earnings guaranteed?

The arithmetic assumes a fixed stated rate and no withdrawal. Whether principal is insured, what limits apply, and what penalties or conditions govern depend on the institution, account ownership and jurisdiction.