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CD Calculator

Find what a certificate of deposit will be worth at maturity, the interest it earns and its APY, from the deposit, rate, term and compounding.

Level: Grades 10–11

  • Common Core standard HSF.LE.A.2Construct linear and exponential functions, including arithmetic and geometric sequences, given a graph, a description of a relationship, or two input-output pairs (include reading these from a table).
  • Common Core standard HSA.SSE.B.3.cUse the properties of exponents to transform expressions for exponential functions.
Printable worksheet

CD Calculator

Know the answer you need? Pick an input to work backward.

Inputs

The rate the bank states, before compounding. Not the APY.

Result

Balance at maturity

$10,460.25

A $10,000.00 CD at 4.5% for 12 months matures at $10,460.25, earning $460.25.

Interest earned
$460.25
Annual percentage yield (APY)
4.602%
What the CD pays out at maturity
  • Deposit$10,000.0095.6%
  • Interest$460.254.4%

See the step-by-step solution ↓

Step-by-step solution

  1. Split the yearly rate into 365 parts, because the bank adds interest 365 times a year

    i=0.045365=0.0001232877

  2. Count how many times interest is added: 365 times a year for 12 months (1 years)

    N=365×1=365

  3. Grow the deposit: each time, the balance gains interest on everything already in it, including past interest

    $10,000.00×(1+0.0001232877)365=$10,460.25

  4. Take away your deposit to see the interest you earned

    $10,460.25−$10,000.00=$460.25

  5. Find the APY: what the rate works out to over one full year, once interest on interest is counted

    (1+0.0001232877)365−1=4.6025%

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

Please note: Results are estimates for planning and comparison. Lenders, banks, and tax authorities may round differently or include fees not modeled here, so confirm figures with your provider before deciding.

What this calculator does

See how much your CD will be worth on the day it ends, and how much interest you'll earn. A certificate of deposit (CD) is a savings account with a fixed rate and a fixed end date. You leave a lump sum with the bank for a set time, called the term. In return, the bank pays a rate that doesn't change until the CD matures (reaches its end date).

Enter your opening deposit, the yearly rate, the term and how often the bank compounds interest. Compounding means adding earned interest to your balance, so that interest earns interest too. You'll see the balance at maturity and how much of it is interest.

You'll also see the annual percentage yield (APY). That's the rate restated to include a year of compounding, so you can compare offers fairly.

Where it's used

Why this math matters outside the classroom:

  • One-year certificate. Depositing $10,000 at 4.5% compounded monthly for one year grows to about $10,459.40.
  • Comparing terms. Savers compare a 1-year and a 5-year certificate by the balance each would reach at maturity.
  • Stated rate versus APY. A 4.5% rate compounded monthly works out to an APY of about 4.594%, which is what banks usually advertise.
  • Building a ladder. Savers split a deposit across certificates that mature a year apart and work out each one's value at maturity.

Grade level and standards: Grades 10–11; Common Core State Standards for Mathematics HSF.LE.A.2, HSA.SSE.B.3.c. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Enter the amount you plan to deposit when the CD opens.
  2. Enter the yearly interest rate the bank quotes. If the bank only gives an APY, see the note on the rate below.
  3. Enter the term in months or years. Pick how often interest compounds; you'll find it in the account terms.
  4. Read the balance at maturity, the interest earned and the APY.

What the inputs mean

Annual interest rate
The yearly rate the bank states, before compounding. Banks often advertise the APY instead. If you only have the APY, choose annual compounding and enter the APY as the rate. That gives the same growth over one year.
Term
Rounded to whole months. Common CD terms are 3, 6, 12, 18, 24, 36 and 60 months.
Compounding
How often earned interest is added to your balance, so it starts earning interest too. Daily and monthly compounding are the most common for CDs.

Formula and method

i = r ÷ n
N = n × (months ÷ 12)
Balance = P × (1 + i)^N
Interest = Balance − P
APY = (1 + i)^n − 1

In the formulas, P is your deposit and r is the yearly rate as a decimal (4.5% is 0.045). n is how many times a year interest is added, and i is the rate for each of those times. N is how many times interest is added over the whole term.

Each time interest is added, the balance is multiplied by (1 + i). So after N times, it has grown by (1 + i)^N. The APY uses the same idea for exactly one year. That's why two CDs with the same rate but different compounding have slightly different APYs.

Worked example

You open a 12-month CD with $10,000 at a 4.5% annual rate, compounded daily.

  1. Rate per day: 0.045 ÷ 365 ≈ 0.0001232877.
  2. Periods: 365 × 1 year = 365.
  3. Balance: $10,000 × (1.0001232877)^365 ≈ $10,460.25.
  4. Interest: $10,460.25 − $10,000 = $460.25.
  5. APY: (1.0001232877)^365 − 1 ≈ 4.6025%.

Result: The CD ends at about $10,460.25. That's $460.25 of interest, for an APY of about 4.603%.

Understanding the result

The balance at maturity is what you'd get if you leave the money alone until the end. It also assumes the bank adds the interest to the CD itself.

To compare two CDs, compare their APYs, not their stated rates. The APY already includes the effect of compounding. A longer term usually pays more. But it only makes sense if you're confident you won't need the money early.

Assumptions and limitations

  • The rate stays the same for the whole term, and interest stays in the CD to keep growing.
  • Daily compounding uses 365 days per year.
  • You make no deposits or withdrawals after opening, and no early withdrawal penalty is charged.
  • Nothing is rounded during the math. Banks may round interest to the cent each time they add it, which can shift the result by a few cents.
  • Taxes on interest aren't included. Interest on a CD is generally taxable as you earn it, even if you don't take it out.
  • Early withdrawal penalties aren't included. They're often several months of interest.
  • It doesn't handle step-up, bump-up or variable-rate CDs, where the rate changes during the term.
  • Some CDs pay interest out to a separate account instead of compounding it. For those, use the simple interest calculator.

Frequently asked questions

What is the difference between the interest rate and the APY on a CD?

The interest rate is the yearly rate before compounding. The APY adds in the extra you earn on interest during the year. At 4.5% compounded daily, the APY is about 4.603%. If interest compounds only once a year, the two are equal.

Does compounding frequency make a big difference?

Less than most people expect. On $10,000 at 4.5% for a year, daily compounding earns about $460.25, and yearly compounding earns $450.00. The gap grows with bigger balances, higher rates and longer terms.

What happens when a CD matures?

Most banks give you a short grace period to take the money out or move it. If you do nothing, many CDs renew on their own for the same term. The new rate is whatever the bank offers then, which may be lower or higher than your first rate.

Can I lose money in a CD?

The balance doesn't fall the way an investment can. But taking money out before maturity usually costs a penalty. That can eat into your interest or, in a short CD, into your deposit. And if inflation runs above the CD's rate, your money can buy less at the end than when you started.

How this calculator is checked

Method: Standard compound interest formula B = P(1 + r/n)^(nt) and the APY definition (1 + r/n)^n − 1. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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