Project compound interest growth for your savings, investments, and retirement portfolios. Calculate returns across daily, monthly, quarterly, or annual frequencies and view detailed monthly balances.
Compound interest is interest calculated on the initial principal, which also includes all of the accumulated interest from previous periods. Our free online Compound Interest Calculator shows you how your savings or investments grow over time, allowing you to compare daily, monthly, quarterly, and annual compounding frequencies.
The formula for compound interest is A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the interest rate, n is the compounding frequency per year, and t is the time in years. Compound interest is the engine of long-term wealth building, and this tool models its impact dynamically.
Simple interest is calculated only on the initial principal amount. Compound interest is calculated on the principal plus any accumulated interest from previous periods, meaning your money grows at an accelerating rate.
The Rule of 72 is a quick way to estimate how long it will take to double your investment with compound interest. Divide 72 by your annual interest rate. For example, at an 8% interest rate, your money will double in about 9 years (72 / 8 = 9).
More frequent compounding (e.g., daily or monthly instead of annually) results in faster investment growth because interest is added to the balance more often, allowing you to earn interest on interest sooner.
When making monthly contributions, the formula is more complex as it combines the compound interest formula for the principal and the future value of an annuity formula for the contributions. Our calculator handles this automatically.