Investment Calculator
Project how your investments grow over time — with inflation-adjusted value and benchmark comparisons.
Projected Value in 20 years
$300,851
Total Contributed
$130,000
Investment Earnings
$170,851
Earnings vs. Contributions
131.4%
In today's dollars (inflation-adjusted)
Real future value
$166,574
Real gain (today's $)
$36,574
$300,851 nominally, but with 3% inflation it buys what $166,574 buys today.
What if you'd invested in…?
Same $10,000 start + $500/mo, at historical-average rates.
| Investment | Rate | Value in 20 yr | vs. your rate |
|---|---|---|---|
| Your assumption | 7.0% | $300,851 | — |
| S&P 500 | ~10% | $452,965 | -$152,114 |
| US Treasuries | ~4.5% | $218,617 | +$82,234 |
S&P 500 ≈ 10%/yr and Treasuries ≈ 4.5%/yr are long-run historical averages — not predictions or guarantees.
Milestones
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| 1 | $16,000 | $919 | $16,919 |
| 5 | $40,000 | $9,973 | $49,973 |
| 10 | $70,000 | $36,639 | $106,639 |
| 15 | $100,000 | $86,971 | $186,971 |
| 20 | $130,000 | $170,851 | $300,851 |
How Investment Growth Is Calculated
This calculator projects the future value of a starting principal plus regular monthly contributions, compounded monthly at your chosen annual rate:
FV = P(1+r/n)(nt) + PMT × [(1+r/n)(nt) − 1] / (r/n)
Where P is the starting principal, PMT is the monthly contribution, r is the annual return, n is 12, andt is years.
The inflation-adjusted value discounts the nominal future value back to today's purchasing power: real FV = nominal FV ÷ (1 + inflation)t. This reveals what your money actually buys — a 7% nominal return at 3% inflation is about 3.9% real.
The benchmark comparison shows how the same contributions would grow at the long-run historical averages of the S&P 500 (~10%) and US Treasuries (~4.5%), so you can judge whether your assumed rate is realistic.
Assumes a constant return with no volatility, taxes, or fees. Real investments fluctuate year to year. Past performance does not guarantee future results.
See our full methodology for every formula, data source, and assumption.
Frequently Asked Questions
What rate of return should I assume?
How are investment returns calculated here?
Why does the inflation-adjusted value matter?
How much do monthly contributions matter?
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Explains index fund investing in plain English — the vehicle that makes the 7% return in our calculator realistic for most people.
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Projections only. Investments can lose value. Past performance does not guarantee future results. Consult a financial advisor for personalized advice.