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Simple Interest Calculator - Calculate Simple Interest Online

A Simple Interest Calculator is a basic financial tool for calculating interest earned or paid on a principal amount over a certain period. In simple interest, the interest is calculated only from the original principal and does not compound over time. This calculator is useful for short-term loans, basic savings scenarios, and educational purposes when learning the fundamentals of interest calculations.

Simple Interest Formula

B = P × r × tFormula: Final Value = P + B

Variables:

  • BInterest Value
    Interest Value(e.g.: $500)
  • PPrincipal - Initial amount of money
    Principal - Initial amount of money(e.g.: $10,000)
  • rInterest Rate per period (%) - in decimal
    Interest Rate per period (%) - in decimal(e.g.: 0.05 (5% per year))
  • tTime - in years or months
    Time - in years or months(e.g.: 2 years)

Categories:

DepositsSimple interest for time deposits
LoansPersonal loans, unsecured credit
SavingsRegular bank savings

How to Use the Simple Interest Calculator

  1. 1

    Enter Principal

    Enter the initial amount (principal) or loan value.

  2. 2

    Enter Interest Rate

    Enter the annual interest rate percentage (e.g., 5 for 5% per year).

  3. 3

    Enter Time Period

    Enter duration in years or months, matching the rate period.

  4. 4

    View Results

    See total interest and final amount (principal + interest).

Examples

Example 1: 2-Year Time Deposit

Problem:

Deposit $50,000 at 6% simple interest for 2 years. Total interest and final value?

Solution:
  1. 1.P=$50,000, r=0.06, t=2
  2. 2.Interest = 50000×0.06×2 = $6,000
  3. 3.Final = $56,000
Result:Final: $56,000

You earn $6,000 interest over 2 years on a $50,000 deposit.

Example 2: Personal Loan

Problem:

Borrow $20,000 at 12% for 3 years. Total repayment?

Solution:
  1. 1.Interest = 20000×0.12×3 = $7,200
  2. 2.Total = $27,200
Result:Total: $27,200

A $20,000 loan at 12% simple interest costs $27,200 over 3 years.

Example 3: Education Savings

Problem:

Save $5,000/year at 4% simple interest for 5 years. Total?

Solution:
  1. 1.Principal total = $25,000
  2. 2.Interest per year = $200
  3. 3.Total interest = $1,000
Result:Total: $26,000

Five years of $5,000 deposits at 4% simple interest reach $26,000.

Example 4: Government Bond Coupons

Problem:

Buy $100,000 bond, 7% annual coupon, 3-year tenor. Total coupons?

Solution:
  1. 1.Interest = 100000×0.07×3 = $21,000
Result:Total coupons: $21,000

A $100,000 bond at 7% yields $21,000 in coupons over 3 years.

Frequently Asked Questions

What is simple interest and how is it calculated?
Simple interest is calculated only on the original principal, not on accumulated interest. Formula: Interest = Principal × Rate × Time. Our calculator applies this instantly.
When should I use simple interest for savings or loans?
Use it for fixed-rate products: time deposits, basic personal loans, or short-term investments before committing.
Simple vs compound interest?
Simple interest uses only the principal; compound interest earns interest on interest. Simple suits short terms (1–3 years); compound grows faster long-term.
How do I calculate loan interest with this calculator?
Enter principal, annual rate (%), and term (years). See total interest and total repayment before applying.
Is this accurate for all bank products?
Accurate for simple-interest products. Some deposits use compound interest or tax withholding—use our compound interest calculator for those.
Why calculate simple interest before borrowing or saving?
Understand total loan cost or savings return, compare products, and make informed financial decisions.
Is the KalkuLab simple interest calculator free?
Yes—completely free, no registration, accessible anytime with a user-friendly interface.
How does tax affect deposit interest?
In many countries, interest income is taxable. Deduct your local withholding rate from gross interest for net return (e.g., 20% tax on $1,000 interest = $800 net).

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References