Compute compound growth over time with frequency controls.
The Compound Interest Calculator projects how an investment grows when interest is calculated on both the original principal and the accumulated interest from prior periods. Unlike simple interest (which only earns on the principal), compound interest produces exponential growth over time. The formula is A = P × (1 + r/n)^(n×t) where P is the principal, r is the annual rate, n is the compounding frequency per year, and t is the time in years. This calculator is essential for retirement planning, savings projections, and understanding loan costs.
More frequent compounding produces slightly higher returns. At 8% annual rate on $10,000 for 10 years: annual compounding gives $21,589; monthly gives $22,196; daily gives $22,253. The rate matters far more than frequency.
Divide 72 by the annual interest rate to estimate the years needed to double your investment. At 8% annual return, 72 ÷ 8 = 9 years. At 6%, it doubles in roughly 12 years.
Yes. A credit card balance at 20% annual interest compounded monthly will nearly triple in 6 years without payments. The same math that grows investments works against you on high-interest debt.