💵 Simple Interest Calculator

Calculate simple interest, annual interest, and the total amount from principal, rate, and time.

Try the calculator

The values below are a working example. Change any field to recalculate instantly in your browser.

Formatting only — amounts are not converted using exchange rates.
TOTAL AMOUNT WITH SIMPLE INTEREST$11,800.00
Principal$10,000.00
Interest Earned / Charged$1,800.00
Interest per Year$600.00

Formula & Mathematical Logic

Simple Interest = Principal × Rate × Time / 100

Simple interest is calculated only on the original principal. Add the interest to the principal to obtain the final total. Calculations run locally in your browser.

Worked Example

$10,000 at 6% simple interest for 3 years earns $1,800, producing a total of $11,800.

Frequently Asked Questions

How is this result calculated?

Multiply the principal by the annual rate and the time in years, then divide by 100.

Does Calcixa upload my inputs?

No. Inputs and results remain in your browser and are not sent to a Calcixa server.

CALCIXA PRACTICAL GUIDE

How to use the Simple Interest Calculator

Simple interest calculates interest only on the original principal, so the interest added in one period does not itself earn interest later. It is useful for classroom problems, short agreements, or products that explicitly quote a simple-interest method.

Many real loans and deposits use reducing balances, compounding, fees, or irregular day counts. Confirm the contract method before applying this result to a transaction.

Step-by-step

  1. Enter the original principal.
  2. Enter the annual simple-interest rate.
  3. Express the time in years or convert the agreed period consistently.
  4. Review both interest and total amount, then confirm the agreement uses simple rather than compound interest.

How to read the result

  • Interest grows linearly with principal, rate, and time.
  • Total amount is principal plus calculated interest.
  • Doubling the time doubles simple interest when principal and rate remain fixed.

Common mistakes to avoid

  • Using simple interest for a compound-interest product.
  • Mixing monthly time with an annual rate without conversion.
  • Ignoring fees, repayments, taxes, or changing balances.

Important: This educational estimate is not financial, investment, tax, or lending advice.

More questions about Simple Interest Calculator

What is the main difference from compound interest?

Simple interest always uses the original principal; compound interest periodically adds interest to the balance.

Can simple interest be used for a reducing loan?

Not without adapting for repayments, because the outstanding principal changes through the schedule.

How should months be entered?

Convert months to a fraction of a year unless the agreement defines another convention.

Sources and methodology

Calcixa explains the model, assumptions, and limitations so you can verify the result. See our calculation and tool methodology for rounding, privacy, testing, and correction practices.

Maintained by the Calcixa product team. This page was last updated on 7 September 2026.