CD Calculator

The calculator compounds your deposit with A = P × (1 + r/n)^(n × t), using the rate and the compounding you choose. That is correct when you enter the CD's interest rate together with its compounding frequency. Banks, however, usually headline the APY, and APY already includes compounding.

If you only have the APY, enter it and set compounding to Annually. That reproduces the APY exactly, because APY is the yield over a 365-day period with compounding built in. Choosing Monthly or Daily with an APY counts the compounding twice and overstates your interest.

Take $25,000 in an 18-month CD (enter 1.5 years) at 4.10% APY:

The last row is the same CD described by its interest rate instead. It lands within a few dollars of the first, and the difference comes only from rounding the rate to two decimals.

Enter the term in years. Quarter steps cover the common terms: 0.25 for 3 months, 0.5 for 6 months, 0.75 for 9 months and 1.5 for 18 months. For a 7-month or 13-month special, type the months ÷ 12, for example 0.58 or 1.08.

A short term earns only part of a year's yield. At 4.00% APY, $10,000 earns about $198.04 over 6 months, not $400. When you compare a 6-month offer with a 1-year offer, compare the APYs, then remember that you will need to find a new rate when the short one matures.

The calculator assumes you hold the CD to maturity. To estimate an early withdrawal, run it with the time you have actually held it, then subtract the penalty from your account agreement.

Each bank sets its own penalty. Federal rules set only a minimum: at least 7 days' simple interest on money withdrawn within the first 6 days after deposit. There is no federal maximum.

Say you close the $25,000 CD above after 12 months. Enter 1 year with Annually and the interest earned so far is $1,025. If the agreement charges 90 days' simple interest, that is about $25,000 × 4.10% × 90 ÷ 365 = $252.74, leaving roughly $772.26 of interest. Comparing that figure with what the money could earn elsewhere tells you whether breaking the CD is worth it.

For a rate change partway through, such as a bump-up CD, run the term in two pieces. A $10,000 two-year CD at 3.80% APY is worth $10,380 after year one. If you bump to 4.20% for year two, enter $10,380 at 4.20% for 1 year: the CD matures at $10,815.96, against $10,774.44 with no bump. A renewal works the same way: the maturity value becomes the next deposit.

For large balances, look at the maturity value, not just the deposit. Standard FDIC insurance is $250,000 per depositor, per insured bank, for each account ownership category. If your total at one bank is near that figure, check how your accounts are covered before you add more.