Simple Interest Calculator

Shawn Plummer, CRPC

Chartered Retirement Planning Counselor

Simple Interest Calculator

A simple interest calculator is a tool used to compute the interest earned on a principal amount over a certain period of time, using a fixed interest rate. It calculates interest based on the formula: Interest=Principal×Rate×Time.

What is Simple Interest?

Definition of Simple Interest:

Simple interest is the basic type calculated only on the original principal amount. In other words, it does not consider any interest earned or paid on previous interest (compound interest). It is commonly used in short-term loans and investments where interest accrues over a fixed period.

Helpful Tool: Compound Interest Calculator

Simple Interest Formula:

The simple interest formula is expressed as I = P * R * T, where:

  • “I” represents the interest amount
  • “P” stands for the principal amount (the initial sum of money)
  • “R” denotes the interest rate (expressed as a decimal)
  • “T” signifies the time period (in years)

How to Calculate Simple Interest

Simple interest is calculated using the formula: Simple Interest=Principal×Rate×TimeSimple Interest=Principal×Rate×Time


  • Principal is the initial amount of money.
  • Rate is the interest rate per period.
  • Time is the number of periods the money is borrowed or invested.

Example Calculation:

  1. Principal (P): $1000
  2. Rate (R): 5% per year
  3. Time (T): 3 years

Simple Interest=$1000×5%×3=$150

Simple Interest Over Time

YearInterest at 5%
Simple Interest Calculator

Benefits of Using a Simple Interest Calculator

Accurate Calculations:

A simple interest calculator ensures your calculations’ accuracy, eliminating potential human errors. This precision is vital when making informed financial decisions, as a small mistake can have significant consequences.


A simple interest rate calculator speeds up determining interest amounts, freeing your valuable time for other essential tasks.

Easy Comparison:

A simple interest calculator lets you quickly compare different loan or investment options, enabling you to choose the most suitable option for your financial situation.

How to Use a Simple Interest Calculator

Input the Principal Amount:

Start by entering the initial sum of money you are investing or borrowing.

Enter the Interest Rate:

Next, input the annual interest rate, expressing it as a decimal. For example, if the interest rate is 5%, enter 0.05.

Input the Time Period:

Finally, enter the time period in the years for which the interest will be calculated.

Calculate the Simple Interest:

Once you have input all the required information, the calculator will determine the simple interest amount based on the given parameters.

Helpful Tip: How to calculate interest rate

How To Calculate Interest

Practical Applications of Simple Interest Calculations

  • Savings Accounts: Understand the interest your savings account will earn over a specific period, helping you plan for future expenses or financial goals.
  • Personal Loans: Determine the total interest payable on a short-term loan, allowing you to make informed decisions about repayment schedules and affordability.
  • Investments: Calculate the returns on short-term investments, enabling you to evaluate the profitability of different investment options.

Limitations of Simple Interest Calculations

  • Not Suitable for Compound Interest: Remember that a simple interest rate calculator cannot be used for calculating compound interest, which is more commonly used in long-term loans and investments.
  • Does Not Account for Additional Fees: Simple interest rate calculators only focus on the interest component and do not include other fees or charges associated with a loan or investment.

Our Favorite Rates To Grow Your Money

TermSavings AccountInstitutionAPY
N/AMoney Market AccountUncle Credit Union5.23%
N/ASavings AccountNexBank5.26%
12 MonthsCDBread Savings5.25%
5 YearsFixed AnnuityWichita National6.30%

Disclaimer: This is a comparison review. The Annuity Expert is not associated with a bank or credit union. We aim to help you find the highest interest rates for your savings. We may receive a small referral fee if you purchase something using a link in this guide.


Simple interest is a straightforward way to calculate the interest on a loan or investment. Remember, it’s based on the original principal amount and doesn’t compound. For any questions or to understand how this applies to your financial needs, contact us today for a free quote.

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Shawn Plummer, CRPC

Chartered Retirement Planning Counselor

Shawn Plummer is a Chartered Retirement Planning Counselor, insurance agent, and annuity broker with over 14 years of first-hand experience with annuities and insurance. Since beginning his journey in 2009, he has been pivotal in selling and educating about annuities and insurance products. Still, he has also played an instrumental role in training financial advisors for a prestigious Fortune Global 500 insurance company, Allianz. His insights and expertise have made him a sought-after voice in the industry, leading to features in renowned publications such as Time Magazine, Bloomberg, Entrepreneur, Yahoo! Finance, MSN, SmartAsset, The Simple Dollar, U.S. News and World Report, Women’s Health Magazine, and many more. Shawn’s driving ambition? To simplify retirement planning, he ensures his clients understand their choices and secure the best insurance coverage at unbeatable rates.

The Annuity Expert is an independent online insurance agency servicing consumers across the United States. The goal is to help you take the guesswork out of retirement planning and find the best insurance coverage at the cheapest rates

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