CD calculator

The CD calculator uses an amount, an annual rate, a term in months, compounding, and an optional tax estimate. The default is interest at maturity with no tax withheld. You can add monthly, quarterly, annual, or daily compounding, treat the rate as APY, and enter a tax percent. $10,000 at 5% for 12 months at maturity is $500 of interest and $10,500 at the end.

Input data

The buttons fill the term in months only. They appear above the Term field.

The buttons fill a percent only. They appear above the tax field. That is not a Form 1099. Leave 0 for interest before tax.

This rate is already APY

U.S. banks advertise APY. If the rate is already APY, check the box so the calculator does not compound it again.

Result

Enter the amount, annual rate, term in months, compounding, and an optional tax estimate. The result appears in this panel.

A U.S. CD-style estimate with months and optional compounding. Multi-year savings without a deposit tax field is on compound interest.

How the result is calculated

How the result is calculated
Amount10000
Rate5%
Months12
CompoundingAt maturity
Net500

The CD calculator uses an amount, an annual rate, a term in months, compounding, and an optional tax estimate. At maturity the formula is amount × rate/100 × months/12. With monthly, quarterly, annual, or daily compounding, gross interest is principal × (1 + (rate/100)/n) to the power of (n × years) minus principal, where n is compounding periods per year and years equal months/12. A term that does not fill a whole cycle (for example 4 months with quarterly compounding) still uses that exponent; it is not a bank’s partial-credit schedule. If you check that the rate is APY, the calculator uses (1 + APY/100)^(months/12) and does not compound again. Tax starts at 0. If you enter a percent, the calculator subtracts it once from gross interest, as an estimate, not as a Form 1099. The effective annual rate on the result is (1 + (rate/100)/n)^n − 1 when you compound during the term; at maturity it equals the rate you entered. That is not the return over the months you entered; that share is net interest as a fraction of principal.

At $10,000, 5%, 12 months, at maturity, and 0% tax, interest is $500 and the final amount is $10,500. The same CD with monthly compounding is $511.62 of interest and $10,511.62 at the end. At $20,000, 4%, and 6 months at maturity, interest is $400. An optional 22% tax estimate on $500 of interest is $110, so $390 remains.

Enter the deposit, the rate, the months, compounding, and tax. The buttons above the Term field fill 1, 3, 6, 12, or 24 months only. Choose compounding from the CD disclosure. Leave tax at 0 unless you want a take-home estimate. If the bank quote is APY, open “This rate is already APY” and check the box. Click Calculate and read interest, the final amount, and the effective annual rate before tax.

The compound-interest page next to this one uses years and does not have a CD tax field. Simple interest in years, with no compounding, is on the savings-interest page.

This is a paper estimate, not a bank offer and not FDIC advice. There is no early-withdrawal penalty in the result. Daily compounding uses 365 periods per year, not the calendar days on a statement. A real CD may still quote APY while compounding daily.

Enter 10,000, 5%, and 12 months, leave compounding at maturity and tax at 0. Check $500 and $10,500. Then switch compounding to monthly and compare $511.62.

How to use

  1. In Deposit amount, enter the principal, for example 10,000. The result uses that same currency.
  2. In Annual interest rate (%), enter the nominal rate or the APY from the ad. Term (months) is the CD length. The buttons above Term fill months only.
  3. In Compounding, choose at maturity, monthly, quarterly, annually, or daily (365). If the quote is already APY, open “This rate is already APY” and check the box.
  4. Leave Estimated tax on interest at 0 for a pre-tax figure. Enter 12, 22, or 24 only as a rough ordinary-income estimate, not a filing.
  5. Click Calculate. At 10,000, 5%, 12 months, at maturity, and 0% tax you should see $500 of interest and $10,500 at the end. Monthly compounding on the same inputs is $511.62.

Compounding, APY, and optional tax

A 12-month CD at 5% on $10,000 is $500 at maturity before tax. Monthly compounding on the same nominal rate is $511.62.

maturity
Simple interest: 10,000 × 5% × 12/12 = 500. There is no interest on interest during the term.
APY
If the box is checked, the rate already includes compounding. The calculator uses (1 + APY/100)^(months/12) and does not apply the compounding menu again. The effective annual rate shown in the result is annual, before tax, not the return over the term you entered.
tax
Optional estimate on interest. Default 0. CD interest is usually reported on Form 1099-INT; this field is not withholding at the bank.

Usage examples

Example 1

  • Amount: 10,000
  • Rate: 5%
  • Term: 12 mo.
  • Compounding: at maturity
  • Tax: 0%

Interest 500
Final 10,500

At $10,000, 5%, and 12 months at maturity: $500 of interest before tax and $10,500 at the end.

Example 2

  • Amount: 20,000
  • Rate: 4%
  • Term: 6 mo.
  • Compounding: at maturity
  • Tax: 0%

Interest 400
Final 20,400

At $20,000, 4%, and 6 months at maturity: $400 of interest and $20,400 at the end.

Example 3

  • Amount: 5,000
  • Rate: 6%
  • Term: 24 mo.
  • Compounding: at maturity
  • Tax: 0%

Interest 600
Final 5,600

At maturity: 5,000 × (6/100) × 24/12 = $600, with no compounding during the term.

Example 4

  • Amount: 20,000
  • Rate: 4%
  • Term: 12 mo.
  • Compounding: at maturity
  • Tax: 0%

Interest 800
Final 20,800

At 20,000 and 4% for a full year at maturity, interest is $800 before tax.

Example 5

  • Amount: 10,000
  • Rate: 5%
  • Term: 12 mo.
  • Compounding: monthly
  • Tax: 0%

Interest 511.62
Final 10,511.62

The same $10,000 / 5% / 12 months with monthly compounding: interest is $511.62.

Example 6

  • Amount: 10,000
  • Rate: 5%
  • Term: 12 mo.
  • Compounding: at maturity
  • Tax estimate: 22%

Gross 500
Tax 110
Net 390
Final 10,390

Optional 22% estimate on $500 of interest. This is not a Form 1099 and not bank withholding.

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A flat percent on a gain you type. That page uses Poland’s 19% investment-gain rate, not a Form 1099 and not CD withholding at a U.S. bank.

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Savings interest calculator: principal × (rate/100) × years, with no compounding and no tax. A CD term in months is on this page.

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Compound interest

The compound interest calculator multiplies principal by (1 + rate/100) to the power of years.

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Frequently asked questions

What is a CD calculator on this page?

The calculator estimates certificate-of-deposit style interest from an amount, annual rate, term in months, compounding, and an optional tax percent. At $10,000, 5%, and 12 months at maturity with 0% tax, interest is $500 and the final amount is $10,500. A paper estimate, not a bank offer.

How is CD interest at maturity calculated?

At maturity: $500 of interest and $10,500 at the end, with tax left at 0. 10,000 × 0.05 × 12/12 = 500.

How is interest calculated for a partial year?

$400 of interest and $20,400 at the end. At maturity, half a year is half the annual rate.

When does compounding add interest during the term?

Only if you choose a compounding option other than at maturity. At maturity the calculator uses 5,000 × 0.06 × 24/12 = $600.

How does monthly compounding change a CD estimate?

$511.62 of interest and $10,511.62 at the end, with tax at 0. The effective annual rate before tax is about 5.12%.

How is this different from compound interest?

This page uses a term in months, a CD compounding menu, optional APY, and an optional tax estimate. The compound interest calculator uses principal, rate, and years, without a deposit tax field.

How is this different from savings interest?

On the savings-interest page, gain is principal × (rate/100) × years, with no compounding and no tax. On this page the term is in months, and you can compound during the CD.

Is this the same as a bank CD or APY quote?

No. The calculator does not pull live bank rates or FDIC disclosures. If the quote is already APY, check the APY box, so compounding is not applied twice.

Does this replace a Form 1099 for interest?

No. The optional tax field is a rough take-home estimate. It is not bank withholding and not a filed Form 1099.

What if I enter tax 0?

That is the default on this page. At 10,000, 5%, and 12 months at maturity you keep the full $500 of interest before any filing.

Is the tax field a Form 1099?

No. It is an optional percent on interest. Losses, brackets, and a return sit outside this calculator. CD interest is usually reported on Form 1099-INT.

What if the bank quotes APY?

Leave the annual rate you typed and check “This rate is APY”. The calculator then uses (1 + APY/100)^(months/12) and does not apply the compounding menu again.

Does a blank term mean one year?

No. You must enter the months. The 12 placeholder is a hint, not a default fill.

· Hubert Ligocki

This is a CD-style estimate with the compounding you choose, not a bank offer. Multi-year savings without a deposit tax field is on compound interest.

Knowledge sources

The calculator uses the rate and compounding you enter, then an optional tax estimate. This is not a bank offer.

Page updated October 29, 2026