Compound Interest Calculator
Model how a starting balance plus regular monthly contributions could grow with compounding. Assumes interest compounds monthly.
Savings plan
Why compounding matters
Compound interest means you earn returns not only on your original contributions, but also on the interest those contributions have already earned. The longer your money stays invested, the larger the share of your final balance comes from interest rather than deposits — which is why starting early tends to matter more than starting with a large amount.
No. This is a simplified projection before taxes, account fees, or fund expense ratios, and it assumes a constant annual return, which real investments rarely deliver year to year.
This calculator assumes contributions are added at the start of each month, with interest compounding monthly on the running balance.
That depends entirely on where the money is held — a high-yield savings account, bonds, and stock index funds have very different historical average returns and risk levels.