CD Interest Calculator

How it works

A certificate of deposit is a simple trade: you agree to leave a lump sum with the bank for a fixed term, and the bank agrees to pay a fixed yield the whole time. Because the rate is locked, the math has none of the guesswork a savings account has. Banks advertise CDs by APY, annual percentage yield, and the APY already folds compounding in, so the balance at maturity is a single clean exponent:

• B — balance at maturity
• P — your opening deposit
• APY — the advertised annual percentage yield, as a decimal
• t — the term in years (months ÷ 12)

With the defaults above, $10,000 at 4% APY for 36 months grows to about $11,249, which is $1,249 of interest on top of the money you handed over. The chart plots that growth month by month using the monthly rate equivalent to your APY, so the curve you see lands on the same maturity value to the dollar. Change the deposit, the APY, or the term and every number updates instantly.

✓ Every result is checked against independent reference math. See how we test the calculators →

A worked example: $10,000 in a 3-year CD at 4% APY

Say you have $10,000 sitting in checking and an online bank is offering a 3-year CD at 4% APY. Lock it in and the balance at maturity comes to $11,249: your deposit back plus $1,249 of interest, earned for doing nothing but leaving the money alone for 36 months.

Now compare that to the branch bank down the street quoting 3% on the same term. The same $10,000 grows to only $10,927, which is $927 of interest. The one-point difference in APY is worth $321 over the term, the price of not shopping around for an afternoon.

Term length pulls the same lever. Keep the 4% APY but shorten the CD to 12 months and the interest drops to $400, with the balance landing at $10,400. Swap in your own deposit, rate, and term above to see what the trade between yield and lock-up really pays you.

Squeezing more yield out of the same deposit

CD rates vary far more between banks than most people expect. The branch bank where you already have a checking account is often the worst payer on the street, while online banks and credit unions compete hard on headline APY. At these defaults, a single percentage point of APY is worth a few hundred dollars over the term, money you get for filling in one extra application.

• Shop the term, not just the rate. Promo CDs with odd terms (7, 11, or 13 months) frequently pay more than the standard 12-month product at the same bank.
• Watch the minimum deposit. Some of the best APYs require $500 or $1,000 to open; jumbo tiers above that rarely pay enough extra to matter.
• Consider a ladder. Split the money across 1, 2, and 3 year CDs. One rung matures every year, so you get regular access to cash and a chance to reinvest at whatever rates look like then, instead of betting everything on today’s rate.

The early-withdrawal catch

The fixed rate is the reward for locking the money up, and the early-withdrawal penalty is the enforcement. Break a CD before maturity and the bank typically claws back a slice of interest: a few months’ worth on shorter terms, often six to twelve months’ worth on longer ones. Exit early enough and the penalty can exceed the interest you have earned so far, which means it eats into your original deposit.

Two ways to stay out of that trap. First, match the term to the date you will actually need the money, and when you are not sure, pick the shorter term; a little less yield beats a penalty. Second, look at no-penalty CDs, which pay a slightly lower APY in exchange for letting you walk away after the first week or so.

They behave like a savings account with a rate floor, which is a fair trade in a falling-rate environment.

CD or high-yield savings account?

The honest comparison is not CD versus nothing, it is CD versus a high-yield savings account, and the difference is who carries the rate risk. A savings account floats: the bank can cut the rate any month it likes, and it usually does when the Federal Reserve cuts. A CD transfers that risk to the bank, since your APY is contractual until maturity.

That points to a simple rule. When rates look likely to fall, locking a CD protects yield you would otherwise lose, and the longer the term, the more protection you buy. When rates are rising, a savings account or a very short CD keeps you free to chase the better rates that are coming.

And money you might need on short notice, like an emergency fund, belongs in savings regardless: liquidity is worth more than the extra fraction of a percent.