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Simple Interest Calculator

Estimate interest earned over time when interest is calculated only on the original principal, not on accumulated interest.

Free tool No signup Browser-based calculations Not financial advice

Enter your assumptions

Change the principal, annual rate, time period and currency to update the result instantly.

The starting amount used for the calculation.
Use the nominal annual rate as a percentage.
Whole years for the annual projection table.
Used only to format inputs and results.

Quick scenarios

Use these examples to compare short, medium and longer simple-interest assumptions.

Year-by-year projection

Each row uses the same principal and annual simple-interest amount. Interest does not compound.

Year Principal Interest this year Cumulative interest Final amount

Formula used: Final Amount = Principal + Simple Interest.

Methodology

How this simple interest calculator works

The calculation uses a fixed principal, annual interest rate and time period. It does not reinvest earned interest.

Calculation methodology

The calculator converts the annual interest rate into a decimal, multiplies it by the principal and then multiplies by the number of years. The result is added to the original principal to estimate the final amount.

Results are educational estimates for planning and comparison. They do not include taxes, fees, changing rates, payment schedules or account-specific terms.

Simple interest formula

The core formula is Simple Interest = Principal x Rate x Time.

The final amount is Final Amount = Principal + Simple Interest.

  • Principal is the starting amount.
  • Rate is the annual interest rate written as a decimal.
  • Time is the number of years.

Simple interest example

If the principal is $10,000, the annual interest rate is 5%, and the time period is 5 years, the simple interest is $10,000 x 0.05 x 5 = $2,500.

The final amount is $10,000 + $2,500 = $12,500. The year-by-year table shows the same annual interest added each year.

Simple interest vs compound interest

Simple interest calculates interest only on the original principal. Compound interest calculates interest on both the principal and previously earned interest.

That difference can become meaningful over longer periods. To compare methods, use the Compound Interest Calculator or read the guide to Compound Interest vs Simple Interest.

Next steps

Related calculators and guides

Use these tools when your estimate needs compounding, savings targets, inflation or a deeper comparison of interest methods.

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Compound Interest Calculator

Estimate growth when interest compounds over time.

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Savings Goal Calculator

Work backwards from a target amount to estimate monthly savings.

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Inflation Calculator

Compare purchasing power across time.

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Compound Interest vs Simple Interest

Understand how the two interest methods differ.

Read guide → Guide

Compound Interest Formula

Review the formula used when interest compounds.

Read formula → Guide

How Much to Save Per Month

Connect interest estimates with a savings habit.

Read guide →
FAQ

Simple Interest Calculator FAQ

Use these answers as educational references. The calculator is not financial advice.

Simple interest is interest calculated only on the original principal. The interest already earned does not start earning additional interest.

Use Simple Interest = Principal x Rate x Time. Convert the annual rate to a decimal before multiplying, then add the interest to the principal to estimate the final amount.

No. Simple interest does not compound. Interest is calculated on the original principal for each year in the time period.

You can use it for simple planning examples where interest is based on principal, annual rate and time. Real loans or accounts may include fees, taxes, payment schedules or compounding rules.

Simple interest applies only to the original principal. Compound interest applies to both principal and previously earned interest, so it can grow faster over longer periods.

No. This calculator is an educational planning tool and does not provide financial advice.