Interest Calculator

Compare simple vs compound interest growth and estimate how long it takes to double your money.

Modify the values and click the Calculate button to use this tool.

Simple Interest

Linear interest on principal only.

Modify the values and click the Calculate button to use this tool.

Compound Interest

Interest compounded at selected frequency.

Modify the values and click the Calculate button to use this tool.

Rule of 72

Estimate years to double your investment.

Formula

Simple: I = Prt | Compound: A = P(1 + r/n)^(nt)

How to use

  1. Choose simple or compound interest mode.
  2. Enter principal, rate, and time period.
  3. Use Rule of 72 for quick doubling estimates.

Formulas explained

Simple interest grows linearly; compound interest grows exponentially with compounding frequency.

FAQ

Simple interest is calculated on principal only; compound includes interest on interest.

Related

Compound InterestInvestment