Find out exactly how your savings or investments grow over time with the power of compounding. Add regular monthly contributions, choose your compounding frequency, and see a year-by-year growth chart with a full table. Export to PDF in one click.
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Enter your starting amount, rate and time horizon, then click Calculate Growth to see the power of compounding.
| Year | Total Deposited | Interest Earned | Balance |
|---|
Compound interest is the process of earning interest on both your original principal and on the interest already accumulated. Over long periods, this creates exponential growth: often called the "eighth wonder of the world."
Where P = principal, r = annual rate, n = compounding periods per year, t = time in years, A = final amount.
The second term accounts for regular contributions (PMT) compounding over the same period.
A quick mental shortcut: divide 72 by the annual interest rate to estimate how many years it takes to double your money.
| Annual Rate | Years to Double (Rule of 72) | Exact Years |
|---|---|---|
| 3% | 24 years | 23.4 years |
| 5% | 14.4 years | 14.2 years |
| 7% | 10.3 years | 10.2 years |
| 10% | 7.2 years | 7.3 years |
| 12% | 6 years | 6.1 years |
More frequent compounding produces slightly higher returns because interest starts earning interest sooner. The difference between monthly and daily compounding is small, but the difference between annual and daily compounding on large sums over long periods can be meaningful.
For a $100,000 investment at 7% over 20 years: annually = $386,968; monthly = $401,604; daily = $402,523. The gap between monthly and daily is just $919: but both beat annual compounding by over $15,000.