Compound Interest Calculator
See how your savings or investments grow with compound interest and regular contributions over time.
| Total Contributions | — |
| Total Interest Earned | — |
| Interest as % of Final | — |
| Doubling Time (Rule of 72) | — |
The Power of Compound Interest
Albert Einstein reportedly called compound interest "the eighth wonder of the world." Whether or not he said it, the concept is genuinely powerful: interest earns interest, and over time this creates exponential rather than linear growth.
The Formula
FV = PV × (1 + r/n)^(n×t) + PMT × ((1 + r/n)^(n×t) − 1) / (r/n)
Where: FV = future value, PV = present value (principal), r = annual rate, n = compounding periods per year, t = time in years, PMT = regular contribution.
Starting Early Makes the Biggest Difference
Investing $10,000 at 7% for 30 years grows to ~$76,000. But if you also contribute $500/month, the same 30-year balance becomes ~$680,000 — where roughly 60% is pure interest growth. Starting 10 years later with the same contributions produces only ~$320,000. Time in market matters more than amount.