Investment Growth Calculator

Frequently asked questions

What return rate should I use for planning?

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 and use the inflation toggle to see results in today’s purchasing power.

How does inflation adjustment work?

When enabled, the calculator converts future values to today’s purchasing power using a fixed annual inflation rate. This shows the "real" value of your money. For example, $100,000 in 20 years at 3% inflation has roughly $55,000 in today’s purchasing power.

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. The earlier you start, the more compounding cycles your money experiences.

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 over time?

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.

How does the tax on interest feature work?

The calculator models tax as a simplified annual deduction on interest earned each year. Positive interest in a given year is multiplied by your tax rate and subtracted from the balance. This is an approximation—actual tax treatment depends on your account type (taxable brokerage, tax-deferred IRA/401k, or tax-free Roth). Consult a tax advisor for your specific situation.

What does the “What if 5 years earlier” section show?

This section compares your current projection with a scenario where you started investing 5 years earlier with the same inputs. It shows how much more you would have accumulated thanks to extra years of compounding. The difference is often striking and illustrates why starting early—even with smaller amounts—can have a dramatic impact on long-term wealth.

What is the difference between this and the compound interest calculator?

The investment growth calculator is designed for long-term portfolio projections. It includes tax on interest, inflation adjustment to see results in today’s purchasing power, and a “what if you started earlier” motivational comparison. The compound interest calculator is better suited for savings accounts and CDs—it offers APY calculation, continuous compounding, and a simple-vs-compound interest comparison. Choose based on whether you are modeling investments (this page) or savings/deposit products.

What is dollar-cost averaging (DCA)?

Dollar-cost averaging means investing a fixed amount at regular intervals regardless of market price. This strategy reduces the impact of short-term volatility by buying more shares when prices are low and fewer when prices are high. The regular contribution feature in this calculator models a DCA approach—set a monthly or annual amount and let compounding work over your chosen time horizon.

How do fees and expense ratios affect investment growth?

Fund expense ratios and advisory fees directly reduce your effective return. A 1% annual fee on a portfolio averaging 7% growth cuts your effective return to roughly 6%, which over 30 years can reduce your ending balance by 25% or more. When setting the expected annual return in this calculator, subtract estimated fees from the gross return for a more realistic projection.

Should I use a tax-advantaged account like a 401(k) or Roth IRA?

Tax-advantaged accounts let investments grow without annual tax drag. In a traditional 401(k) or IRA, contributions are tax-deductible and growth is tax-deferred until withdrawal. In a Roth IRA, contributions are after-tax but qualified withdrawals are tax-free. If your investments are in a tax-advantaged account, set the tax rate to 0% in this calculator since taxes are deferred or eliminated.