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Project how any investment grows over time with compound returns. Model stocks, ETFs, or any portfolio with regular contributions. We're building this calculator now — check back soon.
Project how any investment grows over time with compound returns. Model stocks, ETFs, or any portfolio with regular contributions. We're building this calculator now — check back soon.
This investment growth calculator projects how a portfolio will grow over time based on your initial lump sum, regular contributions, expected annual return, and investment horizon. It illustrates compound interest — the process by which returns generate their own returns — and shows how dramatically different outcomes emerge from small changes in return rate, contribution amount, or time horizon.
For a lump-sum investment with regular contributions:
FV = P(1 + r)ⁿ + PMT × [((1 + r)ⁿ − 1) / r]
Where P is initial principal, r is periodic return rate, n is number of periods, and PMT is the regular contribution. The calculator computes this monthly for greater accuracy.
With simple growth, $10,000 earning 8% grows by $800 each year — after 30 years, it's $34,000. With compound growth, each year's returns also earn returns. After 30 years at 8% compound, $10,000 becomes approximately $100,627 — nearly 3× more than simple growth.
Nominal returns are what you see quoted; real returns subtract inflation. If your portfolio returns 8% and inflation runs 3%, your real return is approximately 5%. The calculator lets you model either nominal or inflation-adjusted returns.
Divide 72 by your annual return rate to estimate years to double your investment. At 8%, money doubles approximately every 9 years. At 6%, every 12 years. This quick mental math shortcut helps evaluate different return assumptions.
For a diversified US stock portfolio, historical long-term nominal returns average 10% (S&P 500 since 1926), though decade returns vary widely. For a 60/40 stock-bond portfolio, 6–7% nominal is commonly used. For conservative planning, many advisors use 5–6% nominal (3–4% real after inflation).
Research shows lump-sum investing outperforms dollar-cost averaging approximately two-thirds of the time because markets tend to rise over time. However, DCA reduces regret risk. For regular income via salary, automatic DCA through paycheck contributions is the practical optimal approach.
In taxable accounts, qualified dividends and long-term capital gains (held over one year) are taxed at 0%, 15%, or 20% depending on income. Short-term gains are taxed as ordinary income. In traditional IRA/401(k) accounts, gains grow tax-deferred and withdrawals are taxed as ordinary income. Roth accounts provide completely tax-free qualified withdrawals.
At 8% annual return, investing $750/month reaches approximately $1 million in about 30 years. Starting with $10,000 and adding $500/month for 30 years at 8% reaches approximately $763,000. To reach $1 million in 20 years starting from zero, you'd need approximately $1,700/month at 8%.
For retirement-specific projections, use the 401(k) Calculator or IRA Calculator. The Compound Interest Calculator focuses on a single investment with no additional contributions. The FIRE Calculator determines your financial independence number using the 4% safe withdrawal rule.