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Compound Interest Calculator

See how your money grows — project the future value of savings and investments with regular contributions and compounding.

  • No upload
  • Free
  • No signup
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Future value
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  • Starting amount$0
  • Total contributions$0
  • Total interest earned$0

Runs entirely in your browser — nothing is uploaded.

Generated entirely in your browser.

How to use Compound Interest Calculator

  1. Enter your starting amount and how much you'll add each period (your contribution).
  2. Choose how often you contribute — monthly, every two weeks, quarterly or yearly.
  3. Set your expected annual return rate, the number of years to grow, and how often interest compounds.
  4. Read the projected future value at the top, and the split of your contributions versus interest earned below.

Common use cases

  • Retirement planning. See how monthly 401(k) or IRA contributions could grow over 20–40 years, and how much of the final balance is pure compound growth.
  • Saving for a goal. Work out how much to set aside each month to hit a target — a house down payment, a car, or a child's education.
  • Comparing investment returns. See the dramatic long-term difference between a 5% and an 8% annual return to appreciate why fees and rate matter so much.
  • Emergency-fund growth. Project how a high-yield savings account balance grows with regular deposits and interest.

Tips

  • Time is the biggest factor. Starting five years earlier often beats contributing more later — that's the power of compounding.
  • The stock market has historically averaged around 7% real annual return, but any single year can be very different.
  • More frequent compounding helps a little, but your contribution amount and the number of years matter far more.
  • Notice how, over long periods, interest earned can dwarf the money you actually put in.

Troubleshooting

The future value seems too high.
Compound growth looks surprising over long periods — that's real. But remember returns aren't guaranteed and this doesn't adjust for inflation or taxes.
Should I use nominal or real return?
If you want today's-dollars purchasing power, subtract expected inflation (about 2–3%) from your return rate before entering it.

Frequently asked questions

What is compound interest?
It's interest earned on both your original money and the interest it has already earned. Over time this snowballs, which is why long horizons produce such large balances.
How often should interest compound?
Many accounts compound monthly or daily. More frequent compounding raises the result slightly, but your rate, contributions and time horizon matter far more.
Does this account for inflation or taxes?
No. It shows nominal growth. To estimate real purchasing power, lower your return rate by expected inflation, and remember gains in taxable accounts may be taxed.
What return rate is realistic?
Historically, a diversified stock portfolio has averaged roughly 7% after inflation over the long run, but returns vary widely year to year. Use a rate you're comfortable with.
Is my financial data stored?
No. All calculations happen in your browser and nothing is uploaded or saved.