Compound Interest Calculator

Project investment growth with compound interest, showing the power of compounding over time with detailed projections.

100% client-side No signup Free forever
Future Value $0.00
Total Contributions $0.00
Total Interest Earned $0.00
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How to Use Compound Interest Calculator

  1. Enter your initial investment amount
  2. Set your planned monthly contribution
  3. Input the expected annual interest rate
  4. Choose your investment period in years
  5. Select compound frequency (monthly, quarterly, etc.)
  6. View results and growth chart instantly
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About Compound Interest Calculator

Compound interest—earning interest on interest—is the mathematical engine behind wealth building. Our calculator projects how investments grow over time, demonstrating why starting early and staying invested matters so dramatically.

Calculation Parameters

  • Principal: Your initial investment amount
  • Interest Rate: Annual percentage yield (APY) or expected return
  • Compounding Frequency: How often interest is calculated and added (daily, monthly, yearly)
  • Time Period: Investment duration in years
  • Regular Contributions: Additional deposits made periodically

The Power of Compounding

$10,000 at 7% annual return becomes $19,672 in 10 years and $76,123 in 30 years—without adding a dollar. Adding $200 monthly transforms those numbers to $53,000 and $286,000. Seeing these projections motivates consistent saving. Time is the critical factor; starting early provides an irreplaceable advantage.

Realistic Expectations

Our calculator shows mathematical projections, not guaranteed returns. Stock market returns average ~7-10% historically but vary dramatically year to year. Savings accounts offer lower but stable returns. Use appropriate rates for your investment type and remember that past performance doesn't guarantee future results.

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Frequently Asked Questions

What is compound interest?
Compound interest is "interest on interest" - you earn returns not just on your original investment, but also on accumulated interest. $1,000 at 5% simple interest earns $50/year forever. With compound interest, you'd earn $50 year one, $52.50 year two, etc. - growing exponentially over time.
What is the compound interest formula?
A = P(1 + r/n)^(nt), where A=final amount, P=principal, r=annual rate, n=compounding frequency per year, t=years. For $1,000 at 5% compounded monthly for 10 years: $1,000 × (1 + 0.05/12)^(12×10) = $1,647.01. Our calculator handles this complexity instantly.
How does compounding frequency affect returns?
More frequent compounding = higher returns. $1,000 at 5% for 10 years: annually=$1,628.89, quarterly=$1,643.62, monthly=$1,647.01, daily=$1,648.66. The difference grows with higher rates and longer periods. Our calculator lets you compare different compounding frequencies side-by-side.
What is the Rule of 72?
The Rule of 72 estimates how long to double your money: 72 ÷ interest rate = years to double. At 6% interest: 72/6 = 12 years to double. At 8%: 9 years. It's an approximation but remarkably accurate for rates between 5-15%. Our calculator shows exact doubling time alongside estimates.
How do regular contributions affect compound growth?
Regular contributions dramatically accelerate wealth building through compound interest. $100/month at 7% for 30 years = $122,000+, but you only contributed $36,000! The earlier and more consistently you contribute, the more compounding works for you. Our calculator models regular deposits or withdrawals.
What is the difference between APY and APR?
APR is the simple annual rate; APY (Annual Percentage Yield) accounts for compounding. A 5% APR compounded monthly = 5.116% APY. For savings, look at APY (your true return). For loans, APR is commonly quoted but actual cost depends on compounding. Our calculator converts between both.