CD Calculator
Enter your deposit, rate, and term to see exactly what your Certificate of Deposit will be worth at maturity — including total interest earned and your effective APY. Switch between entering an APY or a nominal rate with a compounding frequency, and view a full growth breakdown.
Quick examples:
The lump sum placed into the CD at opening
The effective yield banks advertise — already includes compounding.
How long the money stays locked in the CD
In APY mode this labels the breakdown periods and sets the equivalent nominal rate.
CD Maturity Results
Maturity Value
Total Interest Earned
Total Deposits
Effective APY
Equivalent Nominal Rate
Growth Over Time
(12 months)Related Calculators
How This Calculator Works
A Certificate of Deposit (CD) is a fixed-term savings product: you deposit a lump sum, the bank pays a fixed rate, and your balance compounds until maturity. This calculator takes your deposit, rate, term, and compounding frequency and computes exactly what your CD will be worth at maturity, how much interest it earns, and the effective APY behind it.
Maturity Value
A = P(1 + r/n)^(n·t)
P is your initial deposit, r is the nominal annual rate (as a decimal), n is the number of compounding periods per year, and t is the term in years. The result A is your balance at maturity.
Effective APY
APY = (1 + r/n)^n − 1
APY converts a nominal rate plus a compounding frequency into the single effective yield banks advertise. Solving the other direction for the nominal rate gives r = n[(1 + APY)^(1/n) − 1], which is how the tool shows you the equivalent nominal rate when you enter an APY.
APY vs. APR is the key distinction. The nominal rate (APR) is the stated rate before compounding; the APY is the effective rate after compounding. A 4.50% nominal rate compounded monthly equals an APY of about 4.594%. Because APY already bakes in compounding, in APY mode the maturity value is fixed regardless of the frequency you pick — the frequency only changes the equivalent nominal rate the tool displays and how the breakdown periods are labeled. In nominal mode, the frequency directly drives the math and the resulting APY.
Daily compounding uses a 365-day year. The calculator keeps full precision internally and rounds only for display, so the final row of the growth breakdown reconciles with the hero maturity value within a cent.
Tips for Getting the Most From a CD
Compare on APY, Not the Rate
Two CDs can quote different nominal rates yet pay nearly the same because of compounding. Always compare the advertised APY, since it already reflects how often interest compounds. If a bank only lists a nominal rate, use this tool's nominal mode to convert it to an APY before comparing.
Build a CD Ladder
Instead of locking everything into one term, split your money across CDs that mature at staggered dates. A portion frees up regularly for spending or reinvestment while longer rungs capture higher rates. Laddering balances access to cash with yield without trying to time the market.
Match the Term to Your Timeline
Only commit money you will not need before maturity. Early-withdrawal penalties can wipe out months of interest, so a slightly lower rate on a shorter term you can actually hold often beats a higher rate you might have to break early.
Plan for Maturity in Advance
Many CDs auto-renew at the prevailing rate if you do nothing, which may be lower than what you locked in. Note your maturity date and decide ahead of time whether to roll over, move to a better rate, or withdraw — most banks offer a short grace period to act without penalty.
Common Ways People Use a CD
Parking an Emergency Buffer
SafetyIf you hold cash you will not touch for a year or more, a CD can lock in a guaranteed return that beats a standard savings account. Use the calculator to confirm the interest earned justifies giving up easy access for the term.
Saving for a Known Future Expense
GoalPlanning a wedding, tuition payment, or down payment on a fixed date? Match a CD term to that date so the money matures right when you need it, with a predictable maturity value you can plan around.
Comparing Bank Offers
CompareWhen two institutions advertise different rates, compounding frequencies, or rate types, drop each into the calculator to see which actually pays more at maturity. The effective APY readout makes apples-to-apples comparison easy.
Conservative Slice of a Portfolio
IncomeRetirees and risk-averse savers often keep a portion of their money in fixed-rate instruments. A CD offers a known outcome, and this tool shows exactly how much that slice will grow over the chosen term.
What This Calculator Assumes
To keep results deterministic and evergreen, the calculator models a standard fixed-term CD with these assumptions:
- •Single lump-sum deposit: A traditional CD takes one deposit at opening and adds no further contributions. The tool models exactly that — there are no recurring deposits.
- •Fixed rate for the full term: The rate you enter stays constant. Variable, step-up, and bump-up CDs are not modeled.
- •Interest is reinvested: Earnings compound back into the balance rather than being paid out as they accrue.
- •Held to maturity: The math assumes no early withdrawal, so no early-withdrawal penalty is subtracted.
- •Pre-tax, no fees, no inflation: Results do not deduct taxes on interest, account fees, or adjust for inflation. Daily compounding uses a 365-day year.
- •You supply the rate: The tool never pre-fills a current market rate, tax table, or insurance limit — every result comes from the numbers you enter and timeless compound-interest math.
Disclaimer: This tool provides estimates for personal planning and is not financial, tax, or investment advice. Actual returns depend on your bank's terms, and earnings shown are pre-tax. For significant financial decisions, consult a qualified professional.
Frequently Asked Questions
How is CD interest calculated?
CD interest uses compound interest: A = P(1 + r/n)^(n·t), where P is your deposit, r is the nominal annual rate, n is how many times per year interest compounds, and t is the term in years. Each period, interest is added to the balance so the next period earns interest on a slightly larger amount. The calculator does this automatically and shows both your maturity value and the interest earned. For example, $10,000 at a 4.50% nominal rate compounded monthly for 12 months grows to about $10,459.
What's the difference between APY and interest rate (APR)?
The interest rate (or APR / nominal rate) is the stated annual rate before compounding, while APY (Annual Percentage Yield) is the effective rate after compounding is applied. Banks advertise APY because it reflects what you actually earn. A 4.50% nominal rate compounded monthly equals an APY of about 4.594%. This calculator lets you enter either one and shows you the equivalent of the other, so you always know exactly what you will earn.
What APY should I enter?
Enter the APY your bank or credit union advertises for the specific CD term you are considering. Because rates change constantly and vary by institution, this calculator does not pre-fill a current market rate — you supply your own number. If you only know the nominal rate, switch to "Nominal rate" mode and choose the compounding frequency, and the tool will compute the effective APY for you.
How does compounding frequency affect my CD?
The more often interest compounds, the more you earn from the same nominal rate, because interest starts earning interest sooner. Daily compounding yields slightly more than monthly, which yields more than quarterly or annual. The effect is real but usually small for typical CD rates and terms. Note that if you enter an APY, the maturity value is already fixed regardless of frequency, since APY already accounts for compounding.
Can I add money to a CD after opening it?
Most traditional fixed-term CDs do not allow additional deposits after opening — you lock in one lump sum until maturity. A few banks offer "add-on" CDs that do, but they are the exception. This calculator models a single lump-sum deposit, which matches how the vast majority of CDs work. If you want to keep adding money over time, a high-yield savings account or our Savings Goal calculator is a better fit.
What happens if I withdraw my CD early?
Withdrawing before maturity typically triggers an early-withdrawal penalty, often a set number of months of interest, which varies by bank and term. This calculator assumes you hold the CD to maturity and therefore does not subtract any penalty. If you might need the money sooner, check your bank’s specific penalty terms, since penalties can erase much of the interest earned.
Are CD earnings taxed?
In most cases CD interest is taxable as ordinary income in the year it is credited, even if you do not withdraw it, and your bank generally reports it on a tax form. Because tax rates and rules differ by person and change over time, this calculator shows your pre-tax earnings and does not estimate tax. Treat the interest figure as gross, and consult a tax professional for your situation.
Is my money in a CD safe?
CDs at federally insured banks are generally protected up to applicable government insurance limits, and credit-union share certificates have comparable coverage; exact limits and rules can change, so verify current coverage with your institution. This calculator focuses purely on the growth math and does not model insurance limits. As a fixed-rate product held to maturity, a CD return is predictable, which is exactly what this tool illustrates.
What is a CD ladder?
A CD ladder splits your money across several CDs with staggered maturity dates so that a portion matures regularly while longer-term portions earn higher rates. It balances access to your cash with higher yields. This calculator models a single CD; a dedicated CD ladder calculator (planned separately) is the right tool for laddering scenarios.
Why doesn't the breakdown's last balance exactly match a hand calculation?
Tiny differences come from rounding for display. The calculator keeps full precision internally and only rounds when showing currency to two decimals, so the displayed maturity value and the breakdown final balance reconcile within a cent. Hand calculations that round at each step will drift slightly.