Investment Growth Calculator

Frequently asked questions

How do I use this calculator?

Enter your starting balance in the initial investment field. If you plan to add money regularly, set a contribution amount and choose monthly or annual frequency. The "Contribute at" toggle switches between end-of-period (ordinary annuity) and beginning-of-period (annuity due) deposits. Choose an expected annual return that reflects your portfolio. The S&P 500 has historically returned roughly 10% nominal (7% real after inflation). A diversified stock-and-bond portfolio might target 6–7%, while bonds alone average 3–4%. Be conservative for long-range planning. The optional tax field applies a simplified annual levy on interest only—it does not model capital gains schedules or brackets. Use the inflation checkbox to convert results to today’s purchasing power. The yearly table and chart update automatically so you can compare scenarios quickly.

How do compound returns work?

Compound returns mean your earnings generate their own earnings each period. A 7% annual return on $10,000 earns $700 in year one, but roughly $749 in year two because the base has grown. Over decades this snowball effect dominates total wealth. Consistent contributions amplify compounding through dollar-cost averaging—buying more shares when prices are low and fewer when prices are high. Combined with a long time horizon, even modest monthly deposits can outperform larger lump sums invested for shorter periods. The earlier you start, the more compounding cycles your money experiences. The “What if I started 5 years earlier” callout above illustrates exactly how much additional growth an extra five years can produce with the same inputs.

What is a good annual return for investments?

Historical long-term US equity returns are often cited around 7–10% before inflation. A conservative planning range is 5–7%. Bond portfolios have averaged roughly 3–5%. The right figure depends on your asset mix and risk tolerance.

How does compounding frequency affect returns?

More frequent compounding (e.g. monthly vs annually) slightly increases growth when the nominal rate is the same. For example, $10,000 at 7% compounded annually grows to $19,672 in 10 years, while monthly compounding yields $20,097. The effect is modest compared to time horizon and contribution rate.

Are calculator results guaranteed?

No. This tool uses fixed rates and simplified tax assumptions. Real markets fluctuate, and past returns do not guarantee future performance. Consult a financial professional for advice.

What is the difference between simple and compound interest?

Simple interest is earned only on the original principal. Compound interest is earned on the principal plus previously accumulated interest, so growth accelerates over time. For example, $10,000 at 7% simple interest earns $700 per year, while compound interest earns more each successive year as the base grows.

How much should I invest monthly?

A common guideline is to invest 15–20% of gross income. If your employer matches retirement contributions, invest at least enough to capture the full match before allocating elsewhere. Even smaller amounts benefit from compounding over long horizons.

How much will $10,000 grow in 10 years?

At 7% annual return compounded monthly: 5 years → ~$14,176; 10 years → ~$20,097; 20 years → ~$40,387; 30 years → ~$81,165. These figures assume no additional contributions and no withdrawals.

How much will $100,000 grow in 20 years?

At 7% compounded monthly with no contributions, $100,000 grows to approximately $403,870 in 20 years. Adding $500 monthly raises the total to roughly $664,000. Results depend on actual returns and fees.