Our compound interest calculator shows exactly how much your savings or investments will grow over time with regular monthly contributions. See the power of compounding — the earlier you start, the more your money multiplies. Enter your initial deposit, annual rate, number of years, and optional monthly additions.
What is compound interest?
Compound interest is interest calculated on both your initial principal and the accumulated interest from previous periods. Unlike simple interest (which only earns on the original principal), compound interest grows exponentially — your interest earns interest.
What is the Rule of 72?
The Rule of 72 is a quick mental shortcut to estimate how long it takes to double your money. Divide 72 by your annual interest rate. At a 7% annual return, your money doubles in roughly 72 ÷ 7 ≈ 10.3 years.
How often is interest compounded in this calculator?
This calculator uses monthly compounding, which is the most common method for savings accounts and investment accounts. More frequent compounding (daily vs. monthly) produces slightly higher returns over long periods.
How much should I save each month to retire comfortably?
A common guideline is to save 10–15% of your gross income specifically for retirement. The 50/30/20 rule suggests allocating at least 20% of your after-tax income toward savings and debt repayment combined. Use our Budget Planner to find a realistic savings target for your situation.