Free Compound Interest Calculator — Estimate Future Value Online
A compound interest calculator is a free browser tool that estimates future value, total invested capital, and total interest earned over time. Enter your principal, annual rate, frequency, and contributions to see instant projections with no account and no data sent to any server.
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A compound interest calculator is a free browser tool that estimates how an investment grows over time by earning returns on both the original principal and previously accumulated interest. Enter your starting amount, annual rate, compounding frequency, and optional monthly contributions to project future value and total interest earned. All calculations run entirely in your browser using JavaScript — no uploads, no account, and no data sent to any server.
Unlike most financial apps, this calculator requires no sign-up, never stores your inputs, and delivers results instantly in real time. You can model different scenarios — daily vs. monthly compounding, higher vs. lower contribution rates — without creating an account or being tracked. Close the tab and nothing is retained.
How it works
- Enter your principal, annual rate, and compounding frequency — choose from daily, monthly, quarterly, semi-annual, or annual compounding to match your investment or savings account type.
- Set optional monthly contributions and investment duration — add recurring deposits to model a regular savings plan and define how many years you want to project.
- Review the instant projection — see future value, total invested, total interest earned, a year-by-year breakdown table, and a growth chart comparing principal, contributions, and interest.
When to use this tool
- Projecting how a savings account or CD grows over time at a fixed annual rate with monthly compounding.
- Estimating long-term investment growth when making regular monthly contributions to a brokerage or retirement account.
- Comparing how different compounding frequencies — monthly vs. annual — affect total interest earned over the same period.
- Understanding how interest compounds against you on a loan by running the same numbers on the borrowing side.
- Benchmarking investment growth assumptions alongside financing costs from the Mortgage Calculator or repayment projections from the Loan EMI Calculator.
Frequently asked questions
What is compound interest?
Compound interest is the process where your investment earns returns not only on the original principal, but also on the interest accumulated from previous periods. Over time, this compounding effect accelerates growth because the interest base keeps increasing with each cycle.
How often should interest compound?
More frequent compounding generally produces higher growth over time, but the practical difference between daily and monthly compounding is usually small. Monthly compounding is a common baseline for savings accounts and personal finance planning. Daily compounding provides a slight edge for longer time horizons and higher balances.
What is the Rule of 72?
The Rule of 72 is a quick estimate of how long it takes to double your money: divide 72 by your annual interest rate. For example, at 8% per year, your money doubles in approximately 9 years. It is a useful mental benchmark for rapidly comparing investment opportunities without a calculator.
What is the difference between simple interest and compound interest?
Simple interest is calculated only on the original principal, so the interest amount stays the same each period. Compound interest also includes previously earned interest in the base, so the amount grows each cycle. Over longer periods and higher rates, the gap between the two approaches becomes very significant.
How do regular monthly contributions affect compound growth?
Adding consistent monthly contributions dramatically increases the final value because each new deposit has time to compound on its own. Even modest recurring amounts amplify total growth compared to a one-time lump sum at the same rate and term, making contribution frequency a powerful lever over long horizons.
Is my data safe when using this calculator?
Yes. All calculations run entirely in your browser using JavaScript. No inputs are sent to any server, and nothing is stored when you close the tab. No account or sign-up is required at any point.
Disclaimer
This calculator provides estimates for informational and educational purposes only. Actual investment returns vary based on market conditions, fees, taxes, and other factors. Past performance is not indicative of future results. Consult a licensed financial advisor before making investment decisions.
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- Mortgage Calculator
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