Compound Interest Calculator
See exactly how your money grows over time. Enter your principal, rate, and time — we'll show you the numbers and a visual chart.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. This 'interest on interest' effect makes your money grow exponentially over time, unlike simple interest which only grows linearly.
What is the compound interest formula?
The formula is A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate (decimal), n is how many times interest compounds per year, and t is the time in years.
How often should interest compound for maximum growth?
More frequent compounding means more growth. Daily compounding produces slightly more than monthly, which beats quarterly. However, the difference between daily and monthly compounding is typically very small — under 1% for most real-world scenarios.
What is a good compound interest rate?
US stock market indices have historically averaged 7–10% annually. High-yield savings accounts offer 4–5% (as of 2024). S&P 500 index funds, over long periods, average around 7% inflation-adjusted. For a conservative estimate, use 5–7%.