Compound Interest Calculator
See how your money grows with compound interest. Enter your details below — results update instantly.
Calculator Inputs
Additional amount added each month
Final Balance
$20,097
Total Interest Earned
$10,097
Initial Principal
$10,000
Growth Over Time
Year-by-Year Breakdown
| Year | Balance | Interest Earned |
|---|---|---|
| Year 1 | $10,723 | $723 |
| Year 2 | $11,498 | $1,498 |
| Year 3 | $12,329 | $2,329 |
| Year 4 | $13,221 | $3,221 |
| Year 5 | $14,176 | $4,176 |
| Year 6 | $15,201 | $5,201 |
| Year 7 | $16,300 | $6,300 |
| Year 8 | $17,478 | $7,478 |
| Year 9 | $18,742 | $8,742 |
| Year 10 | $20,097 | $10,097 |
How to Use This Calculator
- 1
Enter your starting balance (principal) — this is the amount you're investing today.
- 2
Enter the annual interest rate — check your savings account, CD rate, or expected investment return.
- 3
Set the time period in years — how long you plan to let the money grow.
- 4
Choose how often interest compounds — daily is highest, monthly is most common.
- 5
Optionally add monthly contributions to see the impact of regular deposits.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, compound interest grows exponentially — your interest earns interest.
How often should interest be compounded?
Daily compounding yields the highest return, followed by monthly, quarterly, and annually. For most savings accounts and investments, monthly compounding is standard. The difference between daily and monthly is typically small.
What is the compound interest formula?
A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate (decimal), n is the number of times interest compounds per year, and t is the time in years.
What is the Rule of 72?
Divide 72 by your annual interest rate to estimate how many years it takes to double your money. At 7% interest, your money doubles in approximately 72 ÷ 7 = 10.3 years.
Can this calculator handle monthly contributions?
Yes. Enter an amount in the 'Monthly Contribution' field and the calculator will include those regular deposits in every compounding period, showing the combined growth of your initial investment plus ongoing contributions.
How accurate is this calculator?
This calculator uses the standard compound interest formula and assumes a fixed interest rate throughout the period. Real-world returns vary. Use this for planning and estimation purposes.
What interest rate should I use?
For high-yield savings accounts, use 4–5% (current rates as of 2024–2025). For a diversified stock portfolio, the S&P 500 historical average is approximately 7% after inflation. For CDs, check current rates at your bank.
Does this work for 401k or Roth IRA projections?
Yes, you can use this calculator to estimate retirement account growth. Enter your current balance as the principal, your expected annual return as the rate, and years until retirement. For 401k-specific calculations, also see our 401k Calculator.