Free investment calculator
Project investment portfolio growth — enter starting amount, monthly contribution, expected annual return, and horizon to see future value, updated live, as you type.
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Hypothetical projection. Excludes taxes, inflation, and fees. Actual investment returns vary.
Results are estimates. Consult a professional.
How the investment calculator works
An investment calculator projects the future value of a lump-sum deposit using compound interest. Enter your initial amount, expected annual return, and time horizon — the calculator applies the compound growth formula to show your estimated ending balance.
Worked example: $10,000 at 8% for 10 years
You invest $10,000 today in a diversified index fund earning an average annual return of 8%. You leave the money untouched for 10 years. What is your ending balance?
Growth of lump-sum investments over 10 years
The table below shows projected ending balances for three common starting amounts at annual returns of 6%, 8%, and 10% over a 10-year period. All figures assume annual compounding and no withdrawals.
| Starting Amount | 6% / yr | 8% / yr | 10% / yr |
|---|---|---|---|
| $5,000 | $8,954 | $10,795 | $12,969 |
| $10,000 | $17,908 | $21,589 | $25,937 |
| $25,000 | $44,771 | $53,973 | $64,844 |
Source: FV = PV × (1 + r)¹⁰; rounded to nearest dollar.
Tips for growing your investment
Getting the inputs right makes your projection far more useful. Here are five evidence-based tips for investors at any stage.
- Be conservative with return assumptions — the long-run U.S. equity real return averages ~7%; projections using 10%+ can produce unrealistically optimistic results.
- Reinvest dividends automatically — dividends historically account for roughly 40% of total equity returns; opting out of DRIP leaves significant compounding on the table.
- Minimize fees relentlessly — a 1% annual expense ratio can reduce a 30-year portfolio by more than 25%; low-cost index funds compound the difference back to you.
- Match time horizon to risk tolerance — higher expected returns come with higher volatility; if your horizon is under five years, prioritize capital preservation over growth.
- Max out tax-advantaged accounts first — investing inside a 401(k) or IRA defers or eliminates taxes on gains, effectively boosting your real return rate.
Accuracy and limitations
This calculator assumes a fixed annual return rate and does not account for year-to-year market volatility, inflation, management fees, taxes on gains, or contribution changes. Real portfolios experience variable returns; actual outcomes will differ from any projection. The result is a mathematical estimate based solely on the inputs provided.
For multi-decade projections, run the calculation at two or three different return assumptions (e.g., 5%, 7%, 9%) to build a range of scenarios rather than relying on a single optimistic number.
Not financial advice — consult a financial professional for your specific situation.
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