Compound Interest Calculator
See how your investments grow over time with the power of compounding
Investment Details
$691,150
$190,000
$501,150
Growth Over Time
FIRE Accumulation Simulator
Try the full FIRE accumulation simulator with Monte Carlo analysis
How to Calculate Your FIRE Number
Learn the math behind financial independence targets
Coast FIRE Explained
How compound growth can let you stop saving early
What Is Compound Interest?
Compound interest is the process of earning returns not only on your original investment but also on the accumulated interest from previous periods. Over time, this creates exponential growth that can dramatically accelerate wealth building. Albert Einstein reportedly called it the “eighth wonder of the world.”
The key variables that determine compound growth are your initial investment, regular contributions, the annual rate of return, the compounding frequency, and time. Even modest monthly contributions can grow to substantial sums given enough years, which is the core principle behind the Coast FIRE strategy—reach a critical portfolio size early, then let compound growth do the rest.
This calculator uses the standard compound interest formula adjusted for periodic contributions. For a more comprehensive analysis that includes inflation adjustments, variable market returns, and withdrawal strategies, try the FIREwiz accumulation simulator or learn how to calculate your FIRE number.