About the CD Calculator
A certificate of deposit is the rare financial product where the math is completely knowable in advance: you lock a deposit for a fixed term at a fixed APY, and the bank guarantees the outcome. That certainty is the product. This calculator gives you the exact dollar answer — interest earned and maturity value — for any deposit, rate, and term, so you can compare offers on numbers instead of marketing.
The two details that decide whether a CD beats a savings account: the term you can genuinely commit to (early withdrawal usually claws back months of interest), and whether the quoted number is APY (includes compounding — use it directly here) or APR (doesn't). Banks must advertise APY, so offers are directly comparable.
Comparing a CD against ongoing monthly investing instead? Model that with our Compound Interest Calculator.
The APY Formula
Because APY already bakes in compounding, the calculation is one clean step:
Maturity Value = Deposit × (1 + APY)^years → Interest = Maturity − Deposit
Worked example: $25,000 at 4.50% APY for 18 months = 25,000 × (1.045)^1.5 = $26,706 — $1,706 in interest. Fractional years matter: notice a 6-month CD earns slightly less than half the 1-year interest, because compounding is front-loaded into time, not split evenly.
What a $10,000 CD Earns (by APY and Term)
Interest earned on $10,000 — multiply proportionally for your amount ($50,000 = 5× the cell):
| APY | 6 months | 1 year | 3 years | 5 years |
|---|---|---|---|---|
| 4.00% | $198 | $400 | $1,249 | $2,167 |
| 4.50% | $223 | $450 | $1,412 | $2,462 |
| 5.00% | $247 | $500 | $1,576 | $2,763 |
| 5.50% | $271 | $550 | $1,742 | $3,070 |
Two patterns worth noticing: at any rate, five years earns more than 5× the one-year interest (compounding), and a half-point of APY on a 5-year CD is worth roughly $300 per $10,000 — which is why shopping rates matters most on long terms.
Early Withdrawal Penalties — The Fine Print That Changes the Math
Break a CD before maturity and the bank typically forfeits a slice of interest: commonly around 3 months' worth on terms under a year, and 6–12 months' worth on longer terms (each bank sets its own schedule — it's in the account disclosure). On a young CD, the penalty can exceed interest earned so far and eat into principal.
Practical defenses: match the term to money you genuinely won't need, or build a 'CD ladder' — split the deposit across 1/2/3-year terms so a rung matures regularly. And remember no-penalty CDs exist at slightly lower APYs; this calculator prices both options so you can see what the flexibility costs.