Compound interest calculator
Simulate investments with monthly deposits and see year-by-year growth.
Project an investment’s growth: initial deposit, monthly contributions, interest rate (monthly or yearly, with correct compound conversion) and time horizon. See the final amount, how much came from your pocket versus from interest, plus a year-by-year table — the best way to visualize the snowball effect.
Frequently asked questions
How is a yearly rate converted to monthly?
By compound equivalence: monthly = (1 + yearly)^(1/12) − 1. A 12% yearly rate equals ~0.949% per month — not 1% — because interest compounds within the year itself.
Do deposits earn interest from month one?
In this simulation, each monthly deposit enters at the end of the month and starts earning the following month — the conservative standard used by financial simulators. The initial deposit earns from the first month.
Does the calculator account for inflation or taxes?
No — the result is gross and nominal. For a real-terms view, use a "net" rate (subtracting investment taxes) and compare the result with expected inflation over the period.