Plug in any starting balance, contribution, return, and time horizon to see the power of compounding.
20 yrs at 6% (monthly compounding).
A tailored PDF showing your final balance, total interest earned, and the full year-by-year growth curve.
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Each period's earnings join the principal, so future earnings are calculated on the larger total.
Doubling the horizon is far more powerful than doubling the rate. Start as early as possible.
Small, regular contributions outperform sporadic large ones thanks to dollar-cost averaging.
The classic compound-interest formula is A = P(1 + r/n)^(n·t) for a lump-sum, where P is principal, r the annual rate, n the compounding frequency, and t the number of years.
This calculator extends that by also adding annual (or monthly) contributions, which compound from the moment they're deposited. The longer you let it run, the more dramatic the curve becomes.
Simple interest is calculated only on the principal. Compound interest is calculated on the principal AND all previously-earned interest, producing exponential growth over time.
Yes, but less than you'd think. At 7% APR over 30 years, monthly compounding produces about 8% more than annual compounding. Daily compounding adds another fraction of a percent.
High-yield savings: 4–5%. Diversified bonds: 3–5%. Stock-index ETFs: ~7–10% long-run nominal. Returns are not guaranteed and vary year to year.
This generic calculator ignores taxes. For tax-advantaged accounts (Roth IRA, 529, 530A) the growth is fully or partially tax-free; for taxable accounts, subtract your marginal capital-gains rate from the assumed return.
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