How much does a 3 month CD earn?

About a quarter of its yearly rate, because certificate rates are quoted per year. $10,000 at 5% APY for 3 months earns $122.72, which is 1.2272% of the deposit. At 4.5% APR compounded monthly it earns $112.92, with $37.50 in the first month and slightly more in each of the next two.

Is a 3 month CD the same as 90 days?

Close, not identical. This page counts a month as a twelfth of a year, so 3 months is a quarter of a year, about 91.25 days. A certificate sold as 90 days earns a fraction less: on $10,000 at 5% APY, 90 days of a 365-day year earns $121.03 against $122.72 here. When the exact day count matters, read the disclosure for how the bank counts days.

What if I keep rolling it over every three months?

Each new term earns whatever rate is offered on the day the last one matures, which is not known today. To see a year at one rate, set the term to 12. To estimate a single renewal, enter the maturity value as the new deposit with the rate you expect.

Can I compare a 3 month CD with longer terms?

Switch Show to Compare terms and the same deposit and rate run over 3, 6, 12, 24, 36 and 60 months side by side. Every row uses the one rate you entered, so put each term's own rate in the field before reading a row as an offer.

3 Month CD Calculator

Work out what a three-month certificate of deposit pays when it matures. This page opens on a 3 month term with the balance listed month by month. Enter the deposit and the rate from the offer, set the toggle to APR or APY to match how it was quoted, and the value at maturity, the interest and the effective yield update as you type. The rate in the answer is the one you enter, and the calculation runs in your browser.

10,000.00 at 4.5% APR for 3 months, compounded monthly10,112.92Interest 112.92 · effective yield 4.593983% APY

Deposit

Rate (%)

Quoted as

Term (months)

Common terms

Compounding

Value at maturityafter 3 months
10,112.92
Interest earnedon 10,000.00 deposited
112.92
Interest a monththe interest earned divided by 3 months
37.64
APYthe effective annual yield, compounding included
4.593983%
APRthe stated annual rate, compounding excluded
4.5%

Show

Balance along the way

Rows

The balance at the end of every month, with the interest earned in that month alone. Compounded monthly, the first month earns the deposit times the stated rate divided by 12, which is also what a certificate that pays its interest out each month pays every month.

Month	Balance	Interest that month	Interest so far
1	10,037.50	37.50	37.50
2	10,075.14	37.64	75.14
3	10,112.92	37.78	112.92

Worked examples

Three 3 month certificates worked through, each one loadable into the fields above. The figures are illustrations of the arithmetic, not rates on offer.

3 months5,000.00 at 4.25%, compounded monthly
5,053.31 · interest 53.31
3 months25,000.00 at 5%, compounded daily
25,314.44 · interest 314.44
3 months1,000.00 at 3.9%, compounded quarterly
1,009.75 · interest 9.75

Common questions

How much does a 3 month CD earn?: About a quarter of its yearly rate, because certificate rates are quoted per year. $10,000 at 5% APY for 3 months earns $122.72, which is 1.2272% of the deposit. At 4.5% APR compounded monthly it earns $112.92, with $37.50 in the first month and slightly more in each of the next two.
Is a 3 month CD the same as 90 days?: Close, not identical. This page counts a month as a twelfth of a year, so 3 months is a quarter of a year, about 91.25 days. A certificate sold as 90 days earns a fraction less: on $10,000 at 5% APY, 90 days of a 365-day year earns $121.03 against $122.72 here. When the exact day count matters, read the disclosure for how the bank counts days.
What if I keep rolling it over every three months?: Each new term earns whatever rate is offered on the day the last one matures, which is not known today. To see a year at one rate, set the term to 12. To estimate a single renewal, enter the maturity value as the new deposit with the rate you expect.
Can I compare a 3 month CD with longer terms?: Switch Show to Compare terms and the same deposit and rate run over 3, 6, 12, 24, 36 and 60 months side by side. Every row uses the one rate you entered, so put each term's own rate in the field before reading a row as an offer.

Exact compound interest arithmetic on the deposit, rate, term and compounding you enter. It cannot know your bank's early withdrawal penalty, fees or tax treatment, and it does not carry any rate of its own.