CD Calculator

What a certificate of deposit is

A certificate of deposit, or CD, is a savings product that pays a fixed rate for a set term. You hand the bank a lump sum, agree to leave it for the full term, and the bank returns your deposit plus interest at maturity. The Consumer Financial Protection Bureau describes a CD as a savings account with a fixed length of time and an early withdrawal penalty. CDs sold by banks carry FDIC insurance up to 250,000 dollars per depositor per bank, and credit union versions carry the same limit through the NCUA.

The trade you make is simple. You give up easy access to the money in exchange for a rate that beats a regular savings account. A five year CD at 5.00 percent turns 10,000 dollars into 12,840.03 dollars by maturity, which is 2,840.03 dollars of interest. The rate is locked the day you open the CD, so a falling rate environment cannot cut your payout.

A CD is not a bond or a mutual fund. The principal is insured and the return is known from the start. That makes it a place for money you will not need for a while but do not want exposed to the stock market.

How the maturity value is calculated

The calculator builds the payout from four inputs: the deposit, the annual rate, the term, and how often interest compounds. The core formula is A equals P times (1 plus r divided by n) raised to the power n times t. P is the deposit, r is the annual rate as a decimal, n is the number of compounding periods in a year, and t is the term in years.

The growth factor (1 plus r divided by n) raised to n times t is the step that rewards patience and frequency. With daily compounding at 5.00 percent, that factor over five years is about 1.2840, so 10,000 dollars grows to 12,840.03 dollars. The exponent n times t is the total number of times interest is added, and more additions mean a slightly larger final sum.

At a zero rate the formula collapses to P divided by the number of periods, which is just the deposit returned with no gain. At any positive rate the maturity value exceeds the deposit by the interest earned, and the difference is what you are shopping for when you compare CDs.

Worked example: 10,000 dollars for five years at 5.00 percent

This table tracks a 10,000 dollar deposit at 5.00 percent compounded daily across the full five year term. The balance grows each year as interest compounds on the prior balance.

By year five the balance reaches 12,840.03 dollars and the interest totals 2,840.03 dollars. The first year adds 512.67 dollars of interest, and later years add more because each gain compounds on the last. The curve is gentle early and steeper late, which is the opposite of an amortizing loan.

APY versus the stated rate

Banks quote the annual percentage yield, or APY, because it is the honest number. APY folds the rate and the compounding frequency into one figure you can compare across banks. The formula is APY equals (1 plus r divided by n) raised to n, minus 1. It comes straight from the Truth in Savings Act, which the Federal Reserve codifies as Regulation DD in 12 CFR part 1030, and the FDIC explains in its compliance manual.

For 5.00 percent compounded daily, APY is (1 plus 0.05 divided by 365) raised to 365, minus 1, which is 5.1267 percent, or 5.13 percent. A bank advertising 5.00 percent daily compounding pays 5.13 percent over a full year. Two CDs with the same headline rate but different compounding can pay different amounts, so APY is the field to compare.

The FDIC states that APY reflects the total interest paid, based on the rate and the frequency of compounding over a 365 day period. That is exactly what the formula above captures.

How compounding frequency changes the payout

Compounding frequency barely moves the result on a short term, but it does move it. This table runs 25,000 dollars at 4.50 percent for three years under five schedules.

Daily compounding pays 3,613.18 dollars of interest, while annual compounding pays 3,529.15 dollars, a gap of 84.03 dollars over three years. Continuous compounding, the mathematical limit, edges out daily by 0.24 dollars. The APY on this CD ranges from 4.59 percent monthly to 4.60 percent continuous. The schedule matters most on large deposits and long terms.

Early withdrawal penalties, taxes, and ladders

Most CDs charge a penalty if you cash out before the term ends. The penalty is usually a few months of interest, and it can eat into principal on an early exit. The disclosure statement lists the penalty, the maturity date, and whether the rate is fixed or variable, which the investor guide from Investor.gov walks through.

Interest from a CD is taxable in the year it is earned, even if you let it ride until maturity. That tax lowers your after tax return, so compare a taxable CD with a municipal bond or a tax sheltered account on an after tax basis. The bank sends a 1099 INT for the interest.

A CD ladder splits one large deposit into several CDs that mature on a staggered schedule. You keep some money liquid every few months while still capturing long term rates. When each rung matures you reinvest it at the then current rate, which softens the blow if rates fall.

CDs next to a savings account and an annuity

A high yield savings account beats a CD on flexibility but usually pays less and can change its rate at any time. A CD locks the rate, which protects you if savings rates drop. Use a savings account for your emergency fund and a CD for money with a known future date, like a tax bill or a tuition payment.

A fixed annuity also promises a set return, but it is an insurance product, not a bank deposit, and the 250,000 dollar FDIC limit does not apply. Annuities can carry surrender charges and fees that a CD does not. The CFPB page on CDs is the place to start before you compare the two.

This calculator assumes a fixed rate, interest compounded on the schedule you pick, and no penalties or taxes taken out. Enter your own numbers to see the exact maturity and APY for the CD you are considering.

How the term length changes the payout

A longer term lets the interest compound on a larger base for more years, so the same deposit and rate produce a much bigger maturity. This table holds the deposit at 10,000 dollars and the rate at 5.00 percent, compounded daily, and stretches the term from one year to ten.

The one year CD earns 512.67 dollars, while the ten year CD earns 6,486.65 dollars, more than twelve times as much on the same deposit. The gain is not linear because each year of interest joins the base that earns the next year of interest. A ten year term at 5.00 percent daily turns 10,000 dollars into 16,486.65 dollars, a rise of 6,486.65 dollars that a lower rate savings account cannot match.

Choose the term to match the date you need the money. A five year CD fits a known 2029 expense, and a ten year CD fits a longer goal such as a child college fund. The calculator lets you test any term up to sixty years to see the full effect of time on a fixed rate CD.