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How to Use
- 1Enter the initial investment (principal).
- 2Set the annual interest rate (%).
- 3Choose how often interest compounds (annually, monthly, daily, etc.).
- 4Enter the investment time period in years.
- 5Optionally add a monthly contribution amount.
- 6See final balance, total interest, and a year-by-year growth table.
About Compound Interest Calculator
The Compound Interest Calculator computes investment growth using the standard compound interest formula: A = P(1 + r/n)^(nt). It supports six compounding frequencies — annually, semi-annually, quarterly, monthly, weekly, and daily — so you can model any savings account, CD, or investment product accurately.
Monthly contributions are factored in using the future value of annuity formula, showing realistic growth for retirement accounts, savings plans, and regular investment strategies. See how even small monthly additions compound dramatically over long time horizons.
The year-by-year growth table breaks down your balance, contributions, and interest earned for each year — making it easy to visualize the exponential growth curve that makes compound interest so powerful. Albert Einstein reportedly called it "the eighth wonder of the world," and the numbers here show why.
Use this calculator to compare savings accounts with different APY rates, model the long-term impact of starting early versus starting late, or estimate how much you need to invest monthly to reach a financial goal. All calculations run locally in your browser.
Frequently Asked Questions
What compounding frequencies are available?
Annually, semi-annually, quarterly, monthly, weekly, and daily.
Does it include monthly contributions?
Yes. You can set a monthly contribution amount and the calculator uses the standard future value of annuity formula.
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods, leading to exponential growth.
What compounding frequency should I choose?
Most savings accounts compound daily or monthly. CDs often compound monthly or quarterly. Choose the frequency that matches your account terms for the most accurate projection.