CD Calculator: APY, Term & Compounding
Use this CD calculator to see what a certificate of deposit will actually earn — the same math as a CD rate calculator or CD interest calculator. Enter your deposit, APY, and term length to see your final balance.
How this calculator works
When a bank quotes APY, the rate already accounts for compounding — so the math collapses to simple exponential growth of your principal. The formulas below mirror what the bank discloses on the certificate's account agreement.
The CD interest formula (APY mode)
- A
- Final balance at maturity
- P
- Principal (your deposit)
- APY
- Annual Percentage Yield as a decimal (4.50% → 0.045)
- t
- Term length in years (12 months → 1, 18 months → 1.5)
If your bank quotes a nominal rate
Switch the "Rate type" selector to Nominal rate. The calculator then applies the standard compound-interest formula A = P × (1 + r/n)n·t with the compounding frequency you choose. Most US banks compound CD interest daily or monthly.
Tax on CD interest
CD interest is taxed as ordinary income at federal level (and in most states) in the year it's credited to your account — even if you don't withdraw it. Your bank issues a 1099-INT for any year you earn $10 or more. Long-term CDs that credit interest annually can create a "phantom income" tax situation, so check the disclosure before locking in.
Source: APY definition and disclosure rules — Truth-in-Savings Act, 12 CFR § 1030 (Regulation DD). CD interest taxation — IRS Publication 550. FDIC insurance limits — FDIC deposit insurance.