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Investment & Retirement

Compound Interest Calculator

See the power of compounding with monthly contributions, multiple compounding frequencies, and regional investment return presets.

This compound interest calculator shows how your money grows over time when returns are reinvested. Enter your starting principal, choose how much to add each month, select your expected annual return rate, and pick your compounding frequency. Return presets include the S&P 500 historical average (10%), Nifty 50 (12%), EU stock market (7%), and bonds (4%). The calculator shows year-by-year growth, separating your contributions from the interest earned — so you can clearly see how much the market added on top of what you invested.

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Set your investment parameters and watch your money grow over time.

How Compound Interest Works

The compound interest formula for a lump sum is:

A = P × (1 + r/n)^(n×t)

Where P = principal, r = annual rate, n = compounding periods/year, t = years. With monthly contributions (PMT), the formula becomes:

A = P(1 + r/n)^(nt) + PMT × [((1+r/n)^(nt) − 1) / (r/n)]

Frequently Asked Questions

Historical averages: S&P 500 ~10%/year (before inflation), total stock market ~9.5%, international stocks ~7%, bonds ~4–5%. India's Nifty 50 has averaged ~12–14% over the past 15 years. For conservative planning, use 6–7% to account for fees, taxes, and inflation.
The difference between monthly and daily compounding is small — on $100,000 at 10% over 30 years, daily compounding adds only ~$3,000 more than monthly. The frequency matters much less than the rate and time horizon. Focus on maximizing contributions and return rate.
Subtract expected inflation (historically ~2.5–3%/year) from your return rate to get the "real return." For example, 10% nominal return − 3% inflation = 7% real return. This gives you the purchasing power in today's dollars.

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