CD Calculator

• Compare banks in seconds

  Change one rate and watch the maturity value move. The dollar gap between two offers is instantly visible.

• Compounding handled for you

  Daily, monthly or quarterly compounding is applied correctly, along with the APY-to-APR conversion most calculators skip.

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  The maths runs as JavaScript on your device. No account, no server call, no record of your deposit amount.

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• How is CD interest calculated?

  CD interest is calculated with the compound interest formula A = P(1 + r/n)^(nt), then subtracting your original deposit. P is the principal, 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. A $10,000 CD at 4.50% APY for 12 months matures at $10,450.00, so the interest is $450.00. The compounding frequency is what makes this different from simple multiplication: interest credited in month one joins the principal and earns interest of its own for the remaining eleven months. Most US banks compound daily, using a 365-day year. If your bank quotes an APY rather than a nominal rate, the compounding is already baked into that figure, so a one-year term at 4.50% APY returns exactly 4.50% and no conversion is needed.

• How to calculate CD interest?

  Take the principal, apply A = P(1 + r/n)^(nt), then subtract the principal to isolate the interest. Work through it in order: convert the quoted rate to a decimal, divide by the number of compounding periods per year, add one, raise the result to the power of n times t, and multiply by your deposit. For $10,000 at 4.50% APY over 12 months with daily compounding, that produces $10,450.00 and therefore $450.00 of interest. One step trips people up: if the rate you were given is an APY, it already includes compounding, so applying the formula again as though it were a nominal rate double-counts it. Convert APY to the nominal rate first, or simply multiply by (1 + APY) when the term is exactly one year.

• How do you calculate interest on a CD?

  Use A = P(1 + r/n)^(nt) and subtract the principal. The four inputs are your deposit, the nominal annual rate as a decimal, the compounding periods per year, and the term expressed in years. A $25,000 deposit at 4.25% APY held for 24 months with daily compounding matures at $27,170.16, which is $2,170.16 of interest. Notice that this is more than twice the first year's interest: each credited amount joins the balance and earns interest for the rest of the term, so the curve steepens as the term runs on. The result is before tax. CD interest is ordinary income in the year it is credited, reported on Form 1099-INT above $10, so your after-tax return will be lower than the figure the formula produces.

• How is interest calculated on a CD compounded daily?

  Daily compounding sets n to 365 in A = P(1 + r/n)^(nt), so the rate is divided into 365 slices and each day's credit earns interest for every remaining day of the term. US banks use a 365-day year rather than a 360-day one. The practical effect is smaller than most people expect at typical CD rates: $10,000 at a 4.40% nominal rate compounded daily produces $10,449.80 over one year, while the same nominal rate compounded annually produces $10,440.00 — a difference of $9.80. The gap widens with both the rate and the term, because each extra compounding period acts on a slightly larger balance. This is exactly why Regulation DD requires banks to disclose APY: it folds the frequency into a single number, so two CDs quoting the same nominal rate but compounding differently become directly comparable.

• How to calculate the interest rate on a CD?

  Work backwards from what the CD actually paid. If you know the maturity value and the deposit, the annualised rate of return is (A ÷ P)^(1/t) − 1, where t is the term in years. A $10,000 CD that matured at $11,411.66 after 36 months returns (11,411.66 ÷ 10,000)^(1/3) − 1, or 4.50% a year. If instead you have a nominal rate and want the effective yield, use APY = (1 + r/n)^n − 1; a 4.40% nominal rate compounded daily works out to 4.50% APY. To go the other direction, APR = n × ((1 + APY)^(1/n) − 1). Which one you need depends on what the bank handed you: APY for comparing offers across institutions, the nominal rate for feeding a calculator that expects one.

• How much does a $10,000 CD earn in a year?

  At 4.50% APY, a $10,000 CD earns $450.00 over twelve months and matures at $10,450.00. Because APY already reflects compounding, a one-year term is the one case where the arithmetic is simply the deposit multiplied by (1 + APY) — no conversion required. Change any input and the answer moves: at 4.00% the same deposit earns $400.00, and holding it for five years at 4.50% produces $12,461.82, or $2,461.82 of interest, because each year's credit earns interest of its own thereafter. Two caveats matter for the number you actually keep. The figure is before tax, and CD interest is ordinary income in the year it is credited. And it assumes the interest stays in the CD — if your bank pays it out to a linked account instead, you earn simple interest and the total is lower.

• Is CD interest taxable?

  Yes. CD interest is taxable as ordinary income in the year it is credited to your account, not the year the CD matures. That distinction matters on multi-year CDs: a five-year CD credits interest annually, and you owe tax on each year's credit even though you cannot touch the money until maturity. Your bank reports the amount on Form 1099-INT once it exceeds $10 in a year. So a $10,000 CD at 4.50% APY earning $450.00 in its first year generates a tax liability on that $450.00 that year, regardless of your access to it. Two exceptions are worth knowing: interest on a CD held inside an IRA is not taxed in the year credited, and an early withdrawal penalty is generally deductible against the interest reported. This is general information, not tax advice — confirm your situation with a professional.

• Can you lose money on a CD?

  Yes, in two specific ways, though neither involves the bank failing. The first is an early withdrawal penalty that exceeds the interest earned. Federal rules permit the penalty to reduce principal, so closing a CD before it has earned enough interest returns less than you deposited. Take $10,000 at 4.50% closed after six months with a six-month penalty: you have earned $227.54, the penalty is $225.00, and you walk away with $10,002.54 — barely above break-even, and a month earlier you would have been below it. The second is inflation: a CD paying less than the inflation rate loses purchasing power even while the balance grows. What you are protected against is the institution failing. Deposits are insured up to $250,000 per depositor, per bank, per ownership category, and accrued interest counts toward that limit.

• What happens when a CD matures?

  At maturity the bank credits the final interest and opens a grace period, typically seven to ten days, during which you can withdraw the money, move it, or change the term without paying a penalty. If you do nothing, most CDs renew automatically into a new term of the same length at whatever the bank's current rate happens to be — which is frequently well below the promotional rate that attracted you originally. A $10,000 CD at 4.50% APY hands you $10,450.00 at maturity; left alone, that full balance rolls into a new CD at a rate you did not choose. The grace period is short and the notice is easy to miss, so diary the maturity date when you open the account rather than relying on the letter arriving. Renewal terms and the length of the grace period are set per institution.

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