Compounding occurs when later growth is calculated on a balance that includes earlier growth. The effect depends on the starting amount, contributions, rate, timing, fees, and how long the process continues.
Begin with a simple annual example
At a constant illustrative 5% annual rate, $1,000 becomes $1,050 after one year. A second year adds $52.50, producing $1,102.50. The additional $2.50 comes from growth on the first year’s $50. This arithmetic assumes no contributions, withdrawals, fees, or taxes.
Match the timing to the model
Monthly and annual compounding conventions can produce different results. Contributions made at the beginning of a period have more time to grow than contributions made at its end. Read a calculator’s assumptions before comparing its output with an account statement.
Separate contributions from growth
Adding $100 per month for 12 months contributes $1,200 regardless of the assumed return. A useful schedule shows deposits separately from modeled growth so you can see which part of the projected balance depends on your own saving.
Treat a constant return as an illustration
Market investments do not produce a guaranteed steady monthly return. Losses, fees, taxes, and withdrawals can change the result. Use several scenarios and avoid presenting the largest projection as an expected outcome.
Choose a practical next action
Set an affordable contribution, understand the account and its risks, and review progress using actual deposits and balances. A forecast is most useful when it supports a decision you can explain and sustain.
Inspect a monthly growth schedule. For the broader learning path, browse the related guides.
Official source
Investor.gov compound-interest calculator. Check current information for the relevant year and your circumstances.