Interest Rate Calculator

Calculate simple interest, compound interest, and compare investment growth scenarios.

savingsInterest Rate Calculator

tune

Interest Details

Interest Type

Principal Amount

Interest Rate (%)

Time Period

Tax Rate (optional)

analytics

Interest Summary

savings

Enter your principal amount and interest rate to see results

info

About Interest Rate Calculator

The Interest Rate Calculator helps you calculate both simple and compound interest on your savings or investments. Enter your principal amount, interest rate, and time period to instantly see how much interest you will earn and the total future value of your investment. It supports multiple time units including years, months, and days, along with various compounding frequencies for compound interest calculations.

Understanding how interest works is essential for making informed financial decisions. This calculator also includes an optional tax rate field so you can see the after-tax return on your investment. Whether you are comparing savings accounts, evaluating fixed deposits, or planning long-term investments, this tool gives you a clear breakdown of your expected returns. All calculations run entirely in your browser with no data sent to any server.

help

How to Use

Choose Interest Type

Select between Simple Interest and Compound Interest. Simple interest is calculated only on the principal amount, while compound interest is calculated on both the principal and accumulated interest.

Enter Details

Input your principal amount and annual interest rate. You can use the preset rate buttons for common rates or type a custom value. Optionally enter a tax rate to see after-tax returns.

Set Time Period

Enter the duration of your investment and choose the unit — Years, Months, or Days. For compound interest, also select the compounding frequency (Monthly, Quarterly, Semi-Annually, or Annually).

Calculate

Click Calculate Interest to see your interest earned, future value, effective annual return rate, and a complete calculation breakdown. If a tax rate is set, after-tax figures are also displayed.

quiz

Frequently Asked Questions

What is the difference between simple and compound interest? expand_more

Simple interest is calculated only on the original principal amount. The formula is I = P x r x t. Compound interest is calculated on both the principal and the accumulated interest from previous periods, using the formula A = P x (1 + r/n)^(n*t). Over time, compound interest grows faster because you earn interest on your interest.

How does compounding frequency affect returns? expand_more

The more frequently interest is compounded, the more interest you earn. For example, monthly compounding (12 times per year) produces a higher return than annual compounding (once per year) at the same nominal interest rate, because interest is added to the principal more often and begins earning additional interest sooner.

What is the tax rate field used for? expand_more

The optional tax rate field lets you estimate how taxes will reduce your interest earnings. When you enter a tax rate, the calculator shows the tax amount on your interest, the interest remaining after tax, and the adjusted future value. This helps you understand your real, after-tax return on investment.

How is the effective annual return rate calculated? expand_more

For simple interest, the effective annual return rate equals the nominal interest rate you entered. For compound interest, it is calculated as (1 + r/n)^n - 1, where r is the annual rate as a decimal and n is the number of compounding periods per year. This tells you the true annual yield accounting for compounding.

Can I calculate interest for periods in days or months? expand_more

Yes. You can enter your time period in Years, Months, or Days. The calculator converts months to years by dividing by 12 and days to years by dividing by 365. This is useful for short-term deposits, savings bonds, or any investment with a non-standard term length.