CD Simple Interest Calculator

Calculate certificate of deposit returns using the simple interest formula. Compare simple interest earnings to compound interest to see the exact dollar difference on your deposit.

Your CD Earnings

Final Balance $10,511.62

Total Interest Earned $511.62

Initial Deposit: $10,000.00
Annual Percentage Yield (APY): 5.00%
CD Term: 12 months
Compounding Frequency: Monthly

What Is a CD Simple Interest Calculator?

A CD simple interest calculator computes the interest earned on a certificate of deposit using the basic formula I = P × r × t, where interest is calculated only on the original deposit and does not compound. While most CDs use compound interest, some fixed-rate CDs and brokered CDs pay simple interest. This calculator helps you estimate returns on simple interest CDs and compare those returns to compound interest alternatives.

Deposit Info

Deposit Amount
APY Rate
Term Length
Compounding

Simple Interest A = P × (1 + r/n)^n×t

Earnings Report

Interest Earned
Final Balance
Growth Chart

Key Benefits of Using a CD Calculator

Calculate the exact dollar amount a simple interest CD earns on any deposit from $1,000 to $500,000
Compare simple interest returns against compound interest returns on the same deposit, rate, and term side by side
Determine how much interest income a brokered CD or non-compounding CD generates over 6 months, 1 year, or 5 years
Estimate monthly interest payments on CDs that pay interest to a linked account instead of reinvesting it into the CD

Simple Interest Formula for CDs

The simple interest formula calculates interest based only on the original principal. Unlike compound interest, earned interest is not added back to the balance. The formula has 3 variables — principal, rate, and time — making it straightforward to compute by hand or with a calculator.

A = P × ( 1 + r / n ) ^{n × t}

Click or tap any variable to see what it means

I Total Interest Earned: The dollar amount of interest the CD earns over the full term. With simple interest, this number grows in a straight line — the same amount of interest accrues each month.
P Principal Deposit: The initial dollar amount placed into the certificate of deposit. Simple interest is always calculated on this original amount, regardless of how much interest has already been earned.
r Annual Interest Rate: The yearly rate expressed as a decimal. A 5.00% annual rate becomes 0.05 in the formula. The rate applies to the original principal only — not to accumulated interest.
t Time in Years: The CD term measured in years. A 6-month term equals 0.5 years, a 9-month term equals 0.75 years, and an 18-month term equals 1.5 years.

Simple interest grows in a straight line. A $10,000 CD at 5% earns exactly $500 per year, every year, for a total of $2,500 over 5 years. Compound interest on the same CD at monthly compounding earns $2,833.59 over 5 years — $333.59 more.

How to Use the CD Simple Interest Calculator

Calculate simple interest on your certificate of deposit in 3 steps. The calculator shows both the simple interest result and a compound interest comparison so you can evaluate both options.

Enter Principal and Rate

Type the deposit amount in dollars and the annual interest rate from your CD offer or statement. For simple interest CDs, the stated rate and the effective rate are identical — no APY conversion is needed.

Set the CD Term

Choose how long the CD will run in months or years. The calculator multiplies the principal by the rate and the time to compute simple interest. No compounding frequency is needed for simple interest.

Compare Simple vs. Compound

Review the simple interest earned and the final balance. The calculator also shows what the same deposit would earn under compound interest at monthly compounding, so you can see the dollar difference between the two methods.

Factors That Affect Simple Interest on a CD

Three factors control the dollar amount of simple interest a certificate of deposit earns. Because there is no compounding, the relationship between each factor and the interest earned is perfectly linear.

Principal Amount

Simple interest scales directly with the deposit. Doubling the deposit from $10,000 to $20,000 at 5% for 1 year doubles the interest from $500 to $1,000. No compounding effect changes this ratio.

Annual Interest Rate

The rate has a one-to-one relationship with interest earned under simple interest. A $10,000 deposit at 6% earns $600 per year, while the same deposit at 4% earns $400. Every 1% increase adds exactly $100 per year per $10,000 deposited.

CD Term Length

Simple interest grows at a fixed rate per year. A $10,000 CD at 5% earns $250 in 6 months, $500 in 1 year, $1,000 in 2 years, and $2,500 in 5 years. The per-year earnings never increase or decrease.

Simple vs. Compound: The Gap

The difference between simple and compound interest widens over time. On a $10,000 deposit at 5%, the gap is $11.62 after 1 year but grows to $333.59 after 5 years (monthly compounding). The longer the term, the more valuable compounding becomes.

Simple vs. Compound Interest: $10,000 at 5% Over Multiple Terms

Daily365/yr

$2,840.25

Monthly12/yr

$2,833.59

Quarterly4/yr

$2,820.37

Annually1/yr

$2,762.82

Dollar difference between simple interest and compound interest (monthly) by term length

CD Simple Interest Calculation Examples

These 4 examples use the simple interest formula I = P × r × t to calculate CD earnings. Each example also shows the compound interest equivalent at monthly compounding so you can see the dollar gap between the two methods.

$20,000 CD — 1 Year at 4.50% (Simple Interest)

Initial Deposit: $20,000
APY: 4.50%
Term: 1 Year
Compounding: Simple (no compounding)

Interest Earned $900.00

Final Balance $20,900.00

$20,000 CD — 5 Years at 4.50% (Simple Interest)

Initial Deposit: $20,000
APY: 4.50%
Term: 5 Years
Compounding: Simple (no compounding)

Interest Earned $4,500.00

Final Balance $24,500.00