See exactly how your money grows over time. Enter your starting amount, monthly contributions, and interest rate to get an instant projection with a year-by-year breakdown.
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Compound interest is interest earned not just on your original investment, but on the interest that investment has already accumulated. Each time interest is calculated, it gets added to your balance, and the next round of interest is calculated on that larger amount. This creates a snowball effect: growth accelerates the longer your money stays invested.
The standard formula for compound interest, extended to include regular monthly contributions, is:
Where A is the future value, P is your initial investment, r is the annual interest rate, n is the number of compounding periods per year, t is time in years, and PMT is your monthly contribution.
Two factors matter more than most people expect: starting early, and contributing consistently. A smaller amount invested for longer will often outgrow a larger amount invested for less time, because compounding needs time to do its work.
Compound interest is interest calculated on both your original investment and the interest that investment has already earned. Over time this creates a snowball effect, because each period's interest is added to the balance that earns the next period's interest.
The standard formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate, n is compounding periods per year, and t is years. Monthly contributions are added using an annuity formula that accounts for each contribution compounding for the time it remains invested.
More frequent compounding produces slightly higher returns because interest starts earning its own interest sooner. Daily compounding will always outperform monthly, quarterly, or annual compounding at the same stated rate, though the practical difference is usually small.
Consistent monthly contributions are usually the single biggest driver of long-term growth, often outweighing the interest rate itself over shorter time horizons. Regularly adding money means more capital compounds for longer.
This tool models compound growth mathematically using a fixed annual rate, which is useful for planning and comparison. Real investments such as stocks or crypto fluctuate, so actual returns will vary and are not guaranteed to match a fixed projection.
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