CD calculator
Enter a deposit, APY, and term to see exactly what a certificate of deposit pays at maturity — then switch to ladder mode to stagger 4–5 CDs so one matures every year.
What is a CD calculator?
A CD calculator shows what a certificate of deposit will be worth at maturity: deposit × (1 + APY) raised to the term in years. Because banks quote APY — which already includes compounding — a $10,000 CD at 4.50% APY is worth exactly $10,450 after 12 months and $10,682.54 after 18 months, no matter whether the bank compounds daily or monthly. Ladder mode splits a lump sum across staggered terms so a rung matures every year.
The growth schedule.
| Period | Deposit | Interest earned | Value | Interest share |
|---|---|---|---|---|
| Month 1 | $10,000 | $37 | $10,037 | 0% |
| Month 2 | $10,000 | $74 | $10,074 | 1% |
| Month 3 | $10,000 | $111 | $10,111 | 1% |
| Month 4 | $10,000 | $148 | $10,148 | 1% |
| Month 5 | $10,000 | $185 | $10,185 | 2% |
| Month 6 | $10,000 | $223 | $10,223 | 2% |
| Month 7 | $10,000 | $260 | $10,260 | 3% |
| Month 8 | $10,000 | $298 | $10,298 | 3% |
| Month 9 | $10,000 | $336 | $10,336 | 3% |
| Month 10 | $10,000 | $374 | $10,374 | 4% |
| Month 11 | $10,000 | $412 | $10,412 | 4% |
| Month 12 | $10,000 | $450 | $10,450 | 4% |
Why CD math starts with APY, not APR.
Banks are required to advertise deposit accounts using APY — annual percentage yield — which already bakes in the effect of compounding. That makes CD math simpler than most people expect: the value at maturity is just your deposit multiplied by (1 + APY) raised to the term in years. A $10,000 CD at 4.50% APY is worth $10,450.00 after one year, $10,682.54 after 18 months, and a $10,000 five-year CD at 4.00% APY grows to $12,166.53. You never need to know whether the bank credits interest daily or monthly — two CDs with the same APY pay the same dollar amount.
APR is different: it's the nominal rate before compounding. If a bank quotes 4.40% APR compounded daily, the effective yield is (1 + 0.044/365)^365 − 1 ≈ 4.50% APY. The converter in the calculator handles this so you can compare a credit-union APR quote against an online bank's APY quote on equal footing.
The catch with CDs is liquidity. Withdraw early and most banks charge a penalty of 3–12 months of interest — about $220 on that $10,000 CD at 4.5% with a 6-month penalty. A ladder solves this: split $25,000 into five $5,000 rungs maturing in 1 through 5 years and one rung comes due every year. At today's rates (roughly 4.4% on 1-year down to 3.85% on 5-year), that ladder blends to about 4.06% APY and grows to roughly $28,134 if every rung is held to maturity.
- V
- Maturity value — what the CD is worth when the term ends
- P
- Principal — your opening deposit
- APY
- Annual percentage yield — the advertised rate — compounding already included
- t
- Term in years — months ÷ 12 (an 18-month CD is t = 1.5)
Six ways to actually use these numbers.
Compare on APY, never APR.
APY includes compounding; APR doesn't. A 4.40% APR compounded daily beats a 4.45% APY quote — it's really 4.50% APY. Use the built-in converter before comparing offers.
Check the penalty before the rate.
A 5-year CD with a 12-month interest penalty can cost more to break than the extra yield is worth. On $10,000 at 4%, twelve months of interest is about $400 forfeited.
Ladder money you might need.
A 5-rung ladder gives you penalty-free access to 20% of the money every year while most of it earns longer-term rates. It's the standard fix for CD lock-up risk.
Mind the $250K FDIC line.
Insurance is $250,000 per depositor, per bank. Laddering $400K? Put rungs at two different banks so every dollar stays covered.
Watch the auto-renewal trap.
Most CDs auto-renew at maturity into the same term at the then-current rate, which is often worse. Calendar the maturity date — grace periods are typically only 7-10 days.
CDs shine when rates are falling.
A CD locks today’s rate for years; HYSA rates float down with every Fed cut. If cuts are expected, lengthening your ladder locks the yield in.