Compound Interest Calculator

See how your money grows over time.

The most powerful force in personal finance is compound interest — money growing on money. Our compound interest calculator shows exactly how your investments can grow: enter your starting balance, monthly contributions, expected annual rate, and number of years, then choose how often interest compounds, from daily to annually. The tool projects your future balance and the total interest earned. Whether you are saving for retirement or a big goal, seeing the long-term numbers motivates smarter saving.

Compound Interest

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How to Use the Compound Interest Calculator

Our free compound interest calculator shows how your investments grow over time. Enter your initial investment, monthly contribution, expected annual return, time period (in years), and compound frequency (daily, monthly, quarterly, or annually). See your final balance, total contributions, and total interest earned.

Example Calculations

  • $10,000 invested, $200/month, 7% return, 20 years, monthly compounding: Final balance = $140,815. Total contributions = $58,000. Interest earned = $82,815. Your money more than doubles!
  • $5,000 invested, $100/month, 8% return, 30 years, daily compounding: Final balance = $199,483. Total contributions = $41,000. Interest earned = $158,483. The power of time and compounding.
  • $25,000 lump sum, $0/month, 6% return, 40 years, annual compounding: Final balance = $257,143. No additional contributions needed — just time and compounding work their magic.

Frequently Asked Questions

What is compound interest in simple terms?
Compound interest is interest earned on both your initial deposit AND the interest that accumulates over time. It's often called "interest on interest." Think of it as a snowball rolling downhill — it gets bigger and bigger as it rolls.

How does compound interest work?
Compound interest means you earn interest on both your original principal AND previously earned interest. Unlike simple interest (which only pays on the principal), compounding creates exponential growth over time. The longer your money compounds, the more dramatic the growth.

How does compounding frequency affect growth?
More frequent compounding (daily vs. annually) results in slightly more growth because interest is calculated on a smaller time interval. Our calculator lets you compare daily, monthly, quarterly, and annual compounding to see the difference for yourself.

What is the formula for compound interest?
The formula is A = P(1 + r/n)^(nt) where P is principal, r is annual rate, n is the number of compounding periods per year, and t is the number of years. Our calculator handles all the math for you.

What is the rule of 72?
The rule of 72 is a quick way to estimate how long it takes money to double. Divide 72 by your annual interest rate. For example, at 8%, your money doubles in about 9 years (72/8 = 9). At 6%, it takes about 12 years (72/6 = 12).

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