Compound Interest Calculator for Certificate of Deposit (CD)
FinanceCalculate CD growth using the compound interest formula, with a full step-by-step worked example.
Value at Maturity
Estimated value when the CD matures
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Finance calculators
This calculator shows how a certificate of deposit grows using the compound interest formula, the same math banks use internally, applied step by step to your own numbers. Enter your deposit amount, annual interest rate, and term in months to see the value at maturity.
Unlike a plain balance projection, compound interest means the interest your CD earns in one month starts earning its own interest the next month, which is why the value grows a little faster than simple interest alone. This calculator assumes standard monthly compounding, the most common convention among banks.
A full worked example, the exact formula broken into its parts, and links to every other calculator in this site's compound interest family are below. If you want more control, including a choice of compounding frequency and a separate APY figure, see the full [CD Calculator](finance/cd-calculator) instead.
The compound interest formula for a CD
The formula is A = P times (1 plus r divided by n), raised to the power of n times t. A is the value at maturity, P is your deposit, r is the annual interest rate as a decimal, n is the number of compounding periods per year, and t is the term in years. This calculator uses n equals 12, standard monthly compounding.
For general compound-growth math beyond CDs specifically, see the Compound Interest Calculator.
Worked example, step by step
Take a 10,000 dollar deposit at 4.8 percent annual interest for a 12 month term:
- Monthly rate: 4.8 percent divided by 12 equals 0.4 percent, or 0.004 as a decimal
- Growth factor: 1 plus 0.004 equals 1.004, raised to the power of 12 (one application per month for 12 months) equals about 1.04907
- Value at maturity: 10,000 times 1.04907 equals 10,490.70 dollars
- Interest earned: 10,490.70 minus 10,000 equals 490.70 dollars
The same formula works for any term. For a 6 month CD at 3 percent on a 5,000 dollar deposit, the value at maturity works out to 5,075.47 dollars.
How this differs from the full CD Calculator
This calculator assumes standard monthly compounding to keep the formula walkthrough simple. If your bank compounds daily, quarterly, semiannually, or annually instead, or if you want a separate effective APY figure to compare against your bank's advertised rate, use the full CD Calculator, which supports all of those directly.
Other compound interest calculators
This calculator is part of a family of compound interest calculators for different use cases, all using the same underlying math applied to different situations:
- Compound Interest Calculator, the general-purpose version, with your choice of compounding frequency and optional monthly contributions
- Savings Account, for a regular savings account with monthly deposits
- Retirement / 401(k), projects a retirement account with regular contributions
- Index Fund / ETF, projects an index fund or ETF investment with regular contributions
- Child Education Fund, projects a dedicated education savings fund
- Business Reinvestment, projects profits reinvested back into a business
- Real Estate Appreciation, projects property value appreciation over time
- Crypto Staking, projects returns from a staking position
- DeFi Yield Farming, projects returns from a DeFi yield farming position
- Forex Trading, projects returns from a periodic forex trading return rate
- Credit Card Debt, shows how unpaid credit card debt compounds if left unaddressed
- Student Loan Debt, shows how unpaid student loan interest compounds over time
Frequently Asked Questions
How is this different from the CD Calculator?
This calculator assumes standard monthly compounding and focuses on walking through the compound interest formula step by step. The full CD Calculator adds a choice of compounding frequency (daily, monthly, quarterly, semiannually, or annually) and a separate effective APY output, for more precise comparisons across banks.
What does the compound interest formula for a CD actually mean?
A equals P times (1 plus r over n) to the power of n times t. In plain terms: your deposit grows by a small percentage every compounding period, and each period's interest is added to the balance before the next period's interest is calculated, which is what makes the growth compound rather than stay flat.
Why does this calculator assume monthly compounding?
Monthly is the most common compounding frequency offered by banks on CDs. If your specific CD compounds on a different schedule, use the full CD Calculator instead, which lets you choose daily, quarterly, semiannual, or annual compounding.
What's the difference between the interest rate and APY?
The interest rate is the stated rate before compounding is applied. APY is the actual annualized return after compounding, and is always equal to or slightly higher than the stated rate. This calculator's Annual Interest Rate field expects the stated rate, not an already-compounded APY figure.
What happens if I withdraw from a CD before maturity?
Most CDs charge an early withdrawal penalty, often calculated as a forfeiture of several months' worth of interest, which can reduce or in some cases exceed the interest earned if withdrawn very early in the term.
Does this work for terms longer than a year?
Yes. Enter the term in months, up to 360 months (30 years), and the formula applies the same way regardless of length.
Is a certificate of deposit the only place this compound interest formula applies?
No. The same formula applies to any account or investment with a fixed rate and regular compounding, which is why this calculator is part of a wider family covering savings accounts, retirement accounts, and other use cases, listed below.
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