CD Calculator

A certificate of deposit is a savings product offered by banks and credit unions. You agree to deposit a fixed sum for a set period of time, called the term, and the bank pays you a guaranteed interest rate in return. Terms typically run anywhere from a few months to five years.

The trade-off is access. Unlike a regular savings account, you generally can't touch the money without paying an early withdrawal penalty. That lack of flexibility is exactly why banks offer higher rates on CDs than on standard savings accounts.

At the end of the term, your CD matures. At that point you can withdraw your original deposit plus the interest earned, roll everything into a new CD, or do a mix of both. Some banks also offer no-penalty CDs, which give you more flexibility but usually come with a lower rate.

A few things worth keeping in mind:

• FDIC insurance covers CD deposits up to $250,000 per depositor, per institution, so your principal is protected at any FDIC-member bank.
• Early withdrawal penalties vary widely. Common penalties range from 90 days of interest up to 12 months of interest, depending on the term length.
• Interest crediting schedules differ too. Some CDs credit interest monthly, others quarterly, and some only at maturity.

To calculate CD interest, you need three numbers: your principal (the amount you deposit), the annual interest rate, and the length of the term. From there, the calculation depends on whether the CD uses simple interest or compound interest, and how often it compounds.

For a quick estimate using simple interest, the formula looks like this:

Interest Earned = Principal × Annual Rate × Term (in years)

So if you deposit $10,000 at a 5% annual rate for 2 years with simple interest, you'd earn $10,000 × 0.05 × 2 = $1,000 in interest, for a total of $11,000.

Most CDs actually use compound interest, which means you earn interest on your interest over time. The compounding frequency, whether daily, monthly, or annually, changes your final number. Even at the same stated rate, a CD that compounds daily will pay slightly more than one that compounds annually.

Use the values below as a quick reference for a $10,000 deposit at 5% over 2 years:

The differences look small here, but they add up meaningfully on larger deposits or longer terms.

When you're shopping for CDs, you'll see two different rate figures: the interest rate (sometimes called the nominal rate) and the APY, which stands for annual percentage yield. They're related but not the same thing.

The interest rate is the base rate the bank uses to calculate how much interest accrues. APY accounts for the effect of compounding over a full year. Because of that, APY is almost always the more useful number when comparing CDs from different banks.

Federal law requires banks to disclose APY on deposit accounts, which makes comparison shopping easier. When two CDs advertise the same interest rate but different compounding frequencies, the one with more frequent compounding will have a higher APY. Always compare APYs, not just the headline rates, to find the best deal.

The formula connecting the two is: APY = (1 + r/n)ⁿ - 1, where r is the annual interest rate and n is the number of compounding periods per year.

The maturity value is the total amount you receive when your CD term ends. It includes your original deposit plus all the interest earned over the life of the CD.

The standard formula for maturity value with compound interest is:

Maturity Value = P × (1 + r/n)^n×t

Where:

• P = Principal (your initial deposit)
• r = Annual interest rate (as a decimal, so 5% becomes 0.05)
• n = Number of compounding periods per year (12 for monthly, 365 for daily)
• t = Term in years

Let's say you deposit $25,000 at 4.75% APY, compounding monthly, for 18 months (1.5 years):

Maturity Value = $25,000 × (1 + 0.0475/12)^12×1.5
= $25,000 × (1.003958)¹⁸
= $25,000 × 1.07441
≈ $26,860.25

That's $1,860.25 in interest on a $25,000 deposit in just 18 months. Not spectacular, but it's guaranteed and risk-free.

Compounding is the reason CDs outperform simple interest savings vehicles over time. Every time interest is credited to your account, that new balance becomes the base for the next calculation. Your interest earns interest.

The more frequently a CD compounds, the faster it grows. Daily compounding gives you a slight edge over monthly, which beats quarterly, which beats annual. In practice, the difference between daily and monthly compounding is usually a few dollars on a typical CD, but over long terms and large balances it starts to matter.

Here's how compounding frequency affects a $50,000 deposit at 5% over 5 years:

Longer terms amplify the compounding effect significantly. A 5-year CD will grow your money considerably more than two back-to-back 2.5-year CDs at the same rate, simply because the compounding has more time to build on itself.

A CD ladder is a strategy where you split your money across multiple CDs with different maturity dates. Instead of locking everything into one long-term CD, you stagger the terms so a portion of your money comes due every year or so.

The benefits are real. You get regular access to a chunk of your funds without triggering early withdrawal penalties, and you can take advantage of higher rates if they rise. You're not betting everything on today's rate environment.

Here's a simple example of a 5-year CD ladder with $25,000 split into five equal portions:

Once CD 1 matures in year one, you roll it into a new 5-year CD. Do the same each year, and eventually every rung of your ladder is a 5-year CD earning the highest rate, but one matures annually. It's a straightforward way to balance liquidity and yield.

To calculate the total return on a CD ladder, run the maturity value formula on each individual CD, then add up the results. Each CD has its own rate and term, so treat them separately.

Here's a clean summary of the formulas you'll use most often when working with CD calculations.

Compound Interest Maturity Value:

A = P × (1 + r/n)^n×t

• A = Maturity value (final amount)
• P = Principal
• r = Annual interest rate (decimal form)
• n = Compounding periods per year
• t = Time in years

Simple Interest:

A = P × (1 + r × t)

APY from Nominal Rate:

APY = (1 + r/n)ⁿ - 1

Interest Earned:

Interest = A - P

When plugging in your numbers, make sure your rate is in decimal form (divide the percentage by 100), and your time matches your compounding period. If you're calculating a 9-month CD, that's 0.75 years, not 9.

Walking through a few concrete examples is the fastest way to get comfortable with these formulas. Here are three scenarios that cover common situations.

Example 1: Short-term CD
You deposit $5,000 into a 6-month CD at 5.20% APY, compounding monthly.

A = $5,000 × (1 + 0.052/12)^12×0.5 = $5,000 × (1.004333)⁶ ≈ $5,130.84

Interest earned: $130.84

Example 2: Long-term CD
You deposit $20,000 into a 5-year CD at 4.50% APY, compounding monthly.

A = $20,000 × (1 + 0.045/12)^12×5 = $20,000 × (1.00375)⁶⁰ ≈ $24,952.54

Interest earned: $4,952.54

Example 3: Jumbo CD
You deposit $100,000 into a 2-year jumbo CD at 5.00% APY, compounding daily.

A = $100,000 × (1 + 0.05/365)^365×2 = $100,000 × (1.000137)⁷³⁰ ≈ $110,512.67

Interest earned: $10,512.67

As you can see, the principal amount has the biggest impact on raw dollar returns. A higher rate obviously helps, but parking a larger sum for a longer period is where the real growth happens. Running these numbers before you commit to any CD makes it easy to compare your options side by side.