CD interest depends on the rate your bank offers, how long you lock your money away, and how much you deposit

A certificate of deposit (CD) earns interest at a fixed rate set by your bank when you open the account. The amount you earn is the rate multiplied by your deposit, divided by the number of days in the year, then multiplied by the number of days your money stays in the CD. In plain terms: a higher rate, a longer term, and a bigger deposit all mean more interest in your pocket.

The catch is that CD rates change constantly. A 5.00% rate this week might be 4.75% next week. Banks also offer different rates for different term lengths — a 3-month CD usually pays less than a 12-month CD from the same bank. And the rate you see advertised online may not be the rate your local branch offers. You have to check the specific bank, the specific term, and the specific day you are looking.

Key Takeaways

  • CD interest is calculated by multiplying your deposit by the annual percentage yield (APY), so a $10,000 CD at 5.00% APY earns roughly $500 per year before any taxes.
  • Longer CD terms usually pay higher rates than shorter ones, but rates vary by bank and change weekly or daily.
  • The interest you earn is taxed as ordinary income in the year you receive it, which reduces your actual take-home amount.
  • Breaking a CD early means paying a penalty that typically erases some or all of the interest you earned, so only lock money away if you will not need it.

How to calculate what a specific CD will earn

The formula is straightforward: multiply your deposit by the APY, then multiply by the fraction of the year your money is in the CD. If you deposit $5,000 in a CD paying 4.50% APY for one full year, you earn $5,000 × 0.045 = $225. If you deposit the same amount for six months, you earn roughly $112.50.

Most banks compound interest daily or monthly, which means they add earned interest back into your account and then pay interest on that interest. The APY (annual percentage yield) already accounts for compounding, so you do not have to calculate it separately — the APY is the real rate you will earn. If a bank shows you an APR (annual percentage rate) instead, ask for the APY, because APR does not include compounding.

Use your bank's website or call them directly to find the exact APY for the term length you want. Do not assume all banks offer the same rate. A 12-month CD at one bank might pay 4.75% while another pays 5.25% for the same term. That 0.50% difference means $50 more per year on a $10,000 deposit.

Why CD rates vary so much between banks

Large national banks often pay lower rates than online banks or credit unions because they have more branches and higher overhead costs. Online banks have fewer expenses and can pass savings to depositors in the form of higher rates. Credit unions sometimes offer competitive rates to members, though membership rules vary.

Banks also adjust rates based on what the Federal Reserve does. When the Fed raises its benchmark interest rate, banks usually raise CD rates within days or weeks. When the Fed cuts rates, CD rates fall. This is why a CD that paid 5.50% six months ago might pay 4.75% now — the Fed lowered rates in between.

The trade-off between term length and interest earned

A 6-month CD typically pays less than a 12-month CD from the same bank. A 12-month CD typically pays less than a 24-month or 5-year CD. Banks offer higher rates for longer terms because they want to keep your money locked in for longer. The longer you commit, the more interest you earn — but you also give up access to your cash.

If you need the money before the CD matures, you will pay an early withdrawal penalty. This penalty is usually a certain number of months of interest. A 12-month CD with a 6-month penalty means you lose six months' worth of interest if you withdraw early. On a $10,000 CD earning 5.00%, that penalty is roughly $250. Some banks charge a flat dollar amount instead, which can be $25 to $500 depending on the bank and term.

Before you choose a longer term for a higher rate, make sure you will not need that money. If you might need it within a year, a shorter-term CD with a smaller penalty is often the safer choice.

How taxes reduce your actual earnings

CD interest is taxed as ordinary income. If you earn $500 in CD interest and you are in the 22% federal tax bracket, you owe roughly $110 in federal tax on that interest. Your state may also tax it. This means your real take-home interest is lower than the rate suggests.

If you are retired or have low income, you might owe no tax on CD interest up to a certain threshold. If you have high income, you might owe more. The only way to know for sure is to talk to a tax professional or use tax software when you file your return.

Some people use CDs inside a traditional IRA or Roth IRA to defer or avoid taxes on the interest. Interest earned in a traditional IRA is not taxed until you withdraw it in retirement. Interest in a Roth IRA is never taxed if you follow the withdrawal rules. This can make a big difference over time, especially if you are locking money away for years.

Comparing CD rates across banks in real time

The best way to find the highest rate is to check multiple banks on the same day. Online banks like Marcus, Ally, and American Express Personal Savings often post rates on their websites. Credit unions list rates on their sites too. National banks like Chase, Bank of America, and Wells Fargo usually have lower rates, but it is worth checking.

Some websites aggregate CD rates from multiple banks, though they may not include every institution. These sites can give you a quick sense of the range, but always verify the rate directly with the bank before you deposit. Rates change frequently, and a rate shown on an aggregator site may be outdated.

When you find a bank with a rate you like, check whether there are any restrictions. Some banks limit how much you can deposit in a CD. Others require a minimum deposit of $500, $1,000, or $25,000. A few offer higher rates if you set up automatic transfers or link a checking account.

What happens to your interest when the CD matures

When your CD term ends, the bank will either automatically renew it at the current rate or move the money to a savings account. Check your CD agreement to see what your bank does. If rates have fallen, you might not want to renew at the new rate — you could move your money to a different bank offering a better rate instead.

The interest you earned is yours to keep. The bank will send you a 1099-INT form in January showing how much interest you earned during the previous year. You use this form to report the interest on your tax return.

Frequently Asked Questions

Can I earn more interest by putting money in multiple CDs instead of one?

No. The total interest you earn depends on the total amount deposited and the rate, not on how many separate CDs you open. A $10,000 CD at 5.00% earns the same interest whether it is one account or split into two $5,000 CDs. However, splitting your money across banks can be useful for FDIC insurance protection, since each bank insures up to $250,000 per depositor.

What is the difference between APY and APR on a CD?

APY (annual percentage yield) includes the effect of compounding — interest paid on interest. APR (annual percentage rate) does not. Banks are required to show you the APY, which is the real rate you will earn. If you see an APR listed, ask the bank for the APY instead, because APY is what matters for comparing CDs.

Do I have to pay taxes on CD interest if I do not withdraw it?

Yes. You owe tax on CD interest in the year you earn it, even if you leave the interest in the account. The bank reports the interest to the IRS on a 1099-INT form, and you must report it on your tax return. The only exception is if the CD is inside a tax-deferred account like a traditional IRA.

Is a CD worth it if rates are going down?

It depends on how long you think rates will fall and how long you can lock your money away. If you believe rates will drop further, locking in the current rate for a longer term protects you. If you think rates might rise soon, a shorter-term CD lets you reinvest at a higher rate when it matures. No one can predict rates with certainty, so choose a term that matches when you will actually need the money.

Can I add more money to a CD after I open it?

Most banks do not allow you to add money to an existing CD. You would have to open a new CD with a new deposit. Some credit unions and smaller banks may allow additions, so ask your bank directly. If you want to add money regularly, a high-yield savings account might be a better choice than a CD.