Investment Growth Calculator

Watch your money's future take shape — enter a few numbers and see exactly how much comes from saving and how much comes from compounding.

📖 How it works & FAQ

Initial investment ($)

Monthly contribution ($)

Annual return (%)

Years to grow

How compound growth works

Compounding means your returns start earning returns of their own. Each month, your balance grows a little, and next month's growth is calculated on that bigger balance. This calculator uses the standard future-value formula with monthly compounding: your initial amount grows by (1 + r)^n, where r is the annual return divided by 12 and n is the number of months, and each monthly contribution grows from the month it is added. Over long periods the curve bends sharply upward — that late-stage acceleration is why starting early matters more than starting big.

Invested vs. growth: the number that motivates

The most useful part of this tool is the split between what you actually put in and what the market added on top. On typical long horizons, growth can end up larger than every dollar you contributed. Seeing that a $500 monthly habit could turn $130,000 of deposits into a substantially larger balance makes the abstract idea of "compound interest" concrete. Everything runs privately in your browser — nothing you type is sent anywhere. These figures are estimates only, not financial, tax, insurance, or legal advice; real returns vary year to year and are never guaranteed.

How to use it

Enter your initial investment — the lump sum you are starting with (zero is fine).
Enter your monthly contribution, the amount you plan to add each month.
Set an expected annual return. Many planners use 6-8% for a diversified stock portfolio before inflation.
Choose how many years the money will grow, and read the three cards: future value, total invested, and growth earned. Results update live as you adjust any input.

FAQ

What return rate should I assume?: A common planning range is 6-8% annually for broad stock index funds and 3-5% for balanced or bond-heavy portfolios. Try a few rates to see a realistic range rather than a single prediction.
Does this account for inflation?: No — results are in nominal dollars. To think in today's purchasing power, subtract expected inflation (about 2-3%) from your return rate and rerun the numbers.
When are contributions applied?: At the end of each month, the standard "ordinary annuity" convention. Contributing at the start of each month would produce a slightly higher balance.
Are taxes and fees included?: No. Fund expense ratios, advisory fees, and taxes on gains all reduce real-world results, so treat the output as an upper-bound estimate.