CD calculator

How does this CD calculator work?

A certificate of deposit pays a fixed rate for a fixed term, and closing it early usually costs a penalty. The calculator answers the two questions that follow. What will it be worth at maturity? And what would I get back if I needed the money sooner? On the default inputs, $10,000 at 4% APY for 12 months is worth $10,400 at maturity. With a penalty of 3 months of interest, closing the CD after 6 months returns $10,098.04.

The CD ladder tab answers a third question: what happens if the deposit is split across several CDs that mature at different times. The table under the calculator lists every month of the term or every rung of the ladder.

How do you calculate CD interest from an APY or a rate?

If the bank quotes an APY, compounding is already built in, so the value after t months is deposit x (1 + APY)^(t / 12). That is why the compounding menu is hidden when you choose APY: any frequency gives the same answer for the same APY.

If the bank quotes an interest rate before compounding, the value is deposit x (1 + r / m)^(m x t / 12) for m compounding periods a year, or deposit x (1 + r x t / 12) when interest is not compounded and is paid at maturity. At 4% on $10,000 for 12 months:

For terms longer than a year, a CD that pays simple interest at maturity falls behind: 4% simple over 24 months gives $10,800, an APY of 3.923%.

How do CD early withdrawal penalties work?

In the US, Regulation DD (Truth in Savings) requires a bank's disclosures for a time account to state that a penalty will or may be imposed for early withdrawal, how it is calculated and the conditions for applying it, according to section 1030.4 as published on the Consumer Financial Protection Bureau's site in November 2026. The penalty itself is set in each CD's own terms. This calculator takes it as a number of months of interest, one way those terms can state it.

Here the penalty is deposit x rate x months / 12: on the default CD, $10,000 x 4% x 3 / 12 = $100. The month-by-month table shows how that plays out:

• after 1 month, $32.74 of interest has been earned, so closing returns $9,932.74, which is $67.26 less than was deposited;
• after 3 months, $98.53 has been earned, still short of the $100 penalty;
• from month 4, interest earned is larger than the penalty.

On a 5-year CD at 3.7% APY with a 6-month penalty, closing after 24 months returns $10,568.69 instead of the $11,992.06 due at maturity. A CD's terms may work the penalty differently, for example on the amount withdrawn or at another rate, so read them before relying on the figure.

Is the money in a CD insured?

In the US, the FDIC lists certificates of deposit among the deposits it covers. Its page on understanding deposit insurance, checked in November 2026, states that deposits are insured up to $250,000 per depositor, per FDIC-insured bank, for each account ownership category, and an FDIC consumer page from June 2026 gives the same $250,000 figure. When a USD balance on this page would pass $250,000 at maturity, the calculator notes it. Holding CDs at different insured banks, or in different ownership categories, changes how much is covered, so check the FDIC's own rules for your accounts.

In the UK, fixed-rate bonds and fixed-term savings accounts are the nearest equivalent. The Bank of England's Prudential Regulation Authority announced on 18 November 2025 that the FSCS deposit protection limit would rise from £85,000 to £120,000 from 1 December 2025, and the FSCS's own site gives the limit as £120,000 per person per firm.

What is a CD ladder, and how do you build one?

A ladder splits one deposit across CDs with different terms, so part of the money comes back at regular intervals instead of all at the end. The default ladder puts $10,000 into five rungs of $2,000:

Together the rungs return $11,191.53, with $1,191.53 of interest, and $2,080 is available after the first year. The APYs here are made-up figures for the example: in practice longer terms can pay more or less than shorter ones, so enter the rates you are actually offered. When a rung matures it can be spent or rolled into a new long CD; the calculator does not model the rollover, because the future rate is unknown.

Worked examples in pounds, euros and dirhams

Fixed-term deposits go by different names, but the arithmetic is the same and nothing is converted between currencies. These rates are illustrations, not quotes.

The pound example would carry a £210 penalty for 3 months of interest. The dirham deposit, quoted as a rate, has an APY of 4.594%; enter that APY with the first option and the value at maturity still rounds to AED 52,297.

How do you calculate a CD in Excel or Google Sheets?

No special function is needed. With the deposit in B1, the APY in B2 and the term in months in B3, =B1*(1+B2)^(B3/12) gives the value at maturity: 10,400 for the default CD. For a rate compounded monthly, use =B1*(1+B2/12)^B3; for daily compounding, =B1*(1+B2/365)^(365*B3/12).

For the penalty, put the months of interest in B4: =B1*B2*B4/12. Copy the maturity formula down a column of months from 1 to the term, subtract the penalty, and you have the same table this page builds under the calculator.

Common CD mistakes

• Compounding an APY again. An APY already includes compounding; treating it as a nominal rate overstates the result.
• Assuming you can always get the money back in full. Early on, the penalty can be bigger than the interest earned, as the default example shows for the first three months.
• Reading the penalty as a fixed amount. Months of interest scale with the deposit and the rate.
• Ignoring what happens at maturity. A CD can renew for another term unless you act, so check its terms before the date.
• Comparing a 12-month APY with a 5-year APY on rate alone. The longer CD ties the money up for longer.

What this calculator leaves out

Each CD keeps one rate for its whole term and interest stays in the account until maturity. The calculator does not model tax on interest, interest paid out monthly instead of added, penalties worked on a different basis, partial withdrawals, step-up or bump-up rates, callable CDs, brokered CDs sold before maturity, or automatic renewal. Deposit insurance limits are noted only for US dollar balances, and only the standard $250,000 figure. For regular deposits rather than one lump sum, use the savings calculator; to convert a quoted rate into an APY first, use the APY calculator.

Glossary

Certificate of deposit (CD): a deposit held for a fixed term at a fixed rate. Term: the length of the CD, here in months. Maturity: the end of the term, when the deposit and interest are paid out or renewed. APY: the yearly rate including compounding. Early withdrawal penalty: the charge for closing a CD before maturity, often stated as months of interest. Time account: Regulation DD's term for an account with a maturity of at least seven days. CD ladder: several CDs with staggered terms. Rung: one CD in a ladder.

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