C
FinanceFree

Simple Interest Calculator

Use this free online simple interest calculator to find the interest, total amount, and maturity value for any loan or investment. Enter principal, rate, and time to get instant results.

Enter Values

$
0%100%
1 year30 years

Result

Enter values above and click Calculate to see your result.

AI Assistant

Ask about this calculator

I can help you understand the simple interest calculator formula, interpret your results, and answer follow-up questions.

Try asking

Formula

Interest = Principal × Rate × Time

Multiply the principal amount by the annual interest rate (as a decimal) and the time in years.

Worked Example

Principal: $1,000, Rate: 5% per year, Time: 3 years Step 1: Convert rate → 5% = 0.05 Step 2: Interest = 1000 × 0.05 × 3 = $150 Step 3: Total = 1000 + 150 = $1,150 Result: Interest = $150, Total = $1,150

What Is Simple Interest?

Simple interest is interest calculated only on the original principal amount, not on any accumulated interest. It grows linearly over time, making it straightforward to calculate and predict. Simple interest is commonly used for short-term loans, car financing, and certain types of bonds.
  • Simple interest grows linearly: $1,000 at 5% earns $50 every year, regardless of how long you hold it
  • The formula I = P x R x T makes it easy to calculate interest mentally for simple scenarios
  • Unlike compound interest, simple interest does not generate "interest on interest"
  • The total amount at the end equals the principal plus all accumulated interest: A = P + I

Simple interest is easier to understand and calculate than compound interest, but it generates lower returns for investors. Most savings accounts and long-term investments use compound interest, while some short-term loans and certificates of deposit use simple interest.

You can also calculate changes using our Compound Interest Calculator or Percentage Calculator.

Frequently Asked Questions

What is simple interest?

Interest calculated only on the original principal, not on accumulated interest. For example, $1,000 at 5% simple interest earns exactly $50 per year, every year.

How is simple interest different from compound interest?

Simple interest is calculated on the principal only and grows linearly. Compound interest is calculated on the principal plus previously earned interest, creating exponential growth. Over long periods, compound interest generates significantly more.

When is simple interest used?

Short-term loans, car loans, Treasury bills, some personal loans, and certain bonds use simple interest. It is simpler to calculate and more predictable than compound interest.

How do I calculate simple interest for months instead of years?

Convert months to years by dividing by 12. For 6 months, use T = 0.5. For example, $1,000 at 5% for 6 months: I = 1000 x 0.05 x 0.5 = $25.

What is the maturity value?

The maturity value is the total amount you receive at the end of the loan or investment period. It equals the principal plus all interest earned: Maturity Value = P + (P x R x T).

Related Calculators

Compound Interest CalculatorPercentage Calculator

Related Guides

How Simple and Compound Interest Work

More Finance Calculators

View all

Compound Interest Calculator

See how your investments grow over time.

ROI Calculator

Measure the return on your investments.

Loan EMI Calculator

Calculate loan EMI and see amortization charts.

Offset Mortgage Calculator

Calculate interest and term savings with an offset mortgage.

Explore Other Categories

Secure and Private

All calculations run locally. Your financial data never leaves your browser.

Precise Financial Calculations Powered by Calculory AI