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Interest Calculator

Calculate compound interest with regular contributions — see how your savings grow over time with the power of compounding

⚠️ Disclaimer: Always double-check your calculations and consult a financial professional before making investment decisions. Actual returns may vary.

📈 Interest Details

💡 How It Works

Compound Interest with Contributions

FV = P(1+r)N + C × (1+r)N − 1⁄r × k

Interest compounds on your principal and accumulated interest. Regular contributions accelerate growth, and contributions made at the beginning of a period earn one extra period of growth compared with end-of-period deposits.

FV = Future value  |  P = Principal  |  C = Contribution  |  r = Rate per period  |  N = Number of periods  |  k = 1 for end, 1 + r for beginning

Inflation Adjustment

Real Value = FV ÷ (1 + i)t

Inflation erodes purchasing power over time. The Real Value shows what your future savings will be worth in today's dollars, accounting for inflation.

i = Annual inflation rate  |  t = Time in years

Quick Example

$10,000 at 5% for 10 years:

Without contributions: $16,470.09
With $200/month: $47,655.95

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Fill in the interest details above and click "Save Calculation"

About the Interest Calculator

An interest calculator shows how your money grows over time through compound interest — what Einstein reportedly called the "eighth wonder of the world." Enter a principal amount, annual interest rate, and time period to see the future value of your investment. Adjust the compounding frequency (daily, monthly, quarterly, yearly) to see how more frequent compounding accelerates growth.

Add regular contributions to model a savings plan — whether you're saving for retirement, a down payment, or an emergency fund. Choose between contributions at the beginning or end of each period (beginning-of-period contributions grow faster because they spend more time earning interest). Our calculator also supports an optional inflation rate to show the real (inflation-adjusted) value of your investment in today's dollars.

Save multiple calculations to compare different scenarios — try varying rates, contribution amounts, or time horizons side by side. All computations run locally on your device, unless data needs to be retrieved from other services, so your financial details never leave your device. Remember that this is a projection tool: actual returns depend on market conditions. Consult a financial advisor before making investment decisions.