See what 90 days in a CD actually earns.
Rate is quoted as
3 months
Common terms
Compounding frequency
$25,000.00 in a 3 months CD at 4.30% APY, compounded daily, grows to $25,264.52 — that’s $264.52 of interest, averaging $88.17 per month.
Balance over the term
| Month | Principal | Interest | Balance |
|---|---|---|---|
| At opening | $25,000.00 | $0.00 | $25,000.00 |
| 1mo | $25,000.00 | $87.86 | $25,087.86 |
| 2mo | $25,000.00 | $176.04 | $25,176.04 |
| 3mo | $25,000.00 | $264.52 | $25,264.52 |
Calculated in your browser using A = P(1 + r/n)nt. Nothing is sent to a server. Figures are before tax; confirm exact terms with your bank.
Formulas and content last reviewed . Bank rates change frequently — confirm current rates directly with your institution.
The short answer
A 3-month CD holds your deposit for about 90 days and pays a fixed rate for that period, after which it matures or renews. On a $25,000 deposit at 4.30% APY the term earns $264.52 and matures at $25,264.52; on $10,000 it earns $105.81. Because the term is short, two things follow that do not apply to longer CDs. First, the interest is small enough that a high-yield savings account paying within about 0.30% of the CD rate will usually leave you better off, since it keeps the money liquid for nothing. Second, the early withdrawal penalty — commonly 90 days of interest, which on a 90-day CD is all of it — can consume the entire return and, at many banks, dip into principal. A 3-month CD is therefore worth opening when the rate clearly beats savings and you are certain of the date you need the money back.
Formula & method
A = P(1 + r/n)^(nt), t = 0.25
The standard compound growth formula with a quarter-year term. Three months is 0.25 years, or 91 days on a daily-compounding basis.
Convert the advertised rate to a decimal and divide by n.
Raise (1 + r/n) to the power of n × 0.25 — roughly 91 daily credits.
Multiply by the deposit for the 90-day maturity value.
Subtract the deposit to isolate the interest the quarter earned.
Compare that figure against three months of high-yield savings interest before committing.
Guide
Type the amount you plan to place for the quarter. Short promotional CDs often carry a higher minimum than the bank's standard terms.
Use the rate quoted specifically for the 3-month term, not the bank's headline rate — the headline usually belongs to a different, longer term.
On 90 days the maturity value looks almost unchanged. The interest figure is the number that tells you whether the term was worth it.
Check the same deposit for three months in a high-yield savings account. If the gap is small, the CD is buying you very little for the loss of access.
Examples
Inputs
Result
A quarter at 4.30% returns $264.52. A high-yield savings account at 4.00% over the same 90 days would pay $246.34 and keep the money available — so the CD is buying $18.18 of extra return in exchange for locking up $25,000. That is a thin trade.
Inputs
Result
On a 3-month CD a 90-day penalty is larger than the interest the CD can possibly have earned before maturity. Federal rules permit the bank to take the difference out of principal, so breaking a short CD early can return less than you deposited. This is the defining risk of the term.
Methodology
Three months is treated as 0.25 years. Banks count actual days, so a 91- or 92-day quarter pays marginally more than shown.
The rate is fixed for the term and interest is retained rather than paid out.
The comparison against savings assumes the savings rate holds for the full quarter. Savings rates are variable and can be cut at any time — that is the one advantage the CD has here.
Penalty figures use a 90-day-interest convention. Some banks charge one month of interest on short terms, others all interest earned; the disclosure states which.
Conventions follow Regulation DD (12 CFR 1030), which governs how US institutions disclose APY on deposit accounts. Deposits at insured institutions are FDIC-protected up to $250,000 per depositor, per bank, per ownership category.
Primary sources
Details
A 90-day interest penalty on a 90-day CD means there is no window in which early withdrawal leaves you ahead. Regulation DD lets institutions take the shortfall from principal, and most reserve the right to.
3-month CDs almost never carry the bank's best rate. Promotional pricing clusters at 6, 7, 11 and 13 months, because those are the terms banks use to attract deposits.
The term auto-renews unless you act. A 3-month CD renewing four times a year gives you four short grace periods to miss — set a calendar reminder for the maturity date the day you open it.
Because the term is under a year, the quoted APY is an annualised figure you will not actually receive. Earning 4.30% APY for three months yields about 1.06% of the deposit, not 4.30%.
Treasury bills at 13 weeks are the direct competitor. They are exempt from state and local income tax, which in a high-tax state can beat a nominally higher CD rate.
How it connects
Applications
Money earmarked for a tax bill, a tuition instalment or a closing date in three months. The date is fixed, so the lock-up costs nothing and the rate is guaranteed.
If you expect rates to move soon, a 3-month CD holds a floor while keeping you three months from a decision — the shortest lock a CD offers.
The honest use of this page is often to talk yourself out of the CD. Run both numbers; on a short term the gap is frequently too small to justify the loss of access.
Related tools
FAQs
About a quarter of the annual rate. At 4.30% APY a $25,000 deposit earns $264.52 over three months and $10,000 earns $105.81. The APY is annualised, so a three-month term delivers roughly 1.06% of the deposit rather than 4.30%.
Security & privacy
Uses the same compound interest and APY conventions as banks under Regulation DD.
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Run your own deposit and compare the quarter's interest against leaving the money liquid.