Investment Calculator
See how a starting balance, regular contributions, and time work together to build long-term wealth.
Your inputs
End balance after 30 years
$613,544
In today's dollars
0.0% of end balance
29.3% of end balance
70.7% of end balance
Annual accumulation
Each bar is your balance at the end of that year in today's dollars, stacked by source.
| Year | Contributions | Interest | Ending balance |
|---|---|---|---|
| 1 | $6,000 | $232 | $6,232 |
| 2 | $6,000 | $683 | $12,915 |
| 3 | $6,000 | $1,166 | $20,082 |
| 4 | $6,000 | $1,684 | $27,766 |
| 5 | $6,000 | $2,240 | $36,005 |
| 6 | $6,000 | $2,835 | $44,841 |
| 7 | $6,000 | $3,474 | $54,314 |
| 8 | $6,000 | $4,159 | $64,473 |
| 9 | $6,000 | $4,893 | $75,367 |
| 10 | $6,000 | $5,681 | $87,047 |
| 11 | $6,000 | $6,525 | $99,572 |
| 12 | $6,000 | $7,431 | $113,003 |
| 13 | $6,000 | $8,401 | $127,404 |
| 14 | $6,000 | $9,443 | $142,847 |
| 15 | $6,000 | $10,559 | $159,406 |
| 16 | $6,000 | $11,756 | $177,162 |
| 17 | $6,000 | $13,039 | $196,201 |
| 18 | $6,000 | $14,416 | $216,617 |
| 19 | $6,000 | $15,892 | $238,508 |
| 20 | $6,000 | $17,474 | $261,983 |
| 21 | $6,000 | $19,171 | $287,154 |
| 22 | $6,000 | $20,991 | $314,145 |
| 23 | $6,000 | $22,942 | $343,087 |
| 24 | $6,000 | $25,034 | $374,121 |
| 25 | $6,000 | $27,278 | $407,399 |
| 26 | $6,000 | $29,683 | $443,082 |
| 27 | $6,000 | $32,263 | $481,345 |
| 28 | $6,000 | $35,029 | $522,374 |
| 29 | $6,000 | $37,995 | $566,368 |
| 30 | $6,000 | $41,175 | $613,544 |
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How this calculator works
This tool projects how a starting balance plus monthly contributions grow over time through compound interest. It uses monthly compounding, with contributions added at the start of each month.
You enter a return net of inflation (a real return), so the ending balance is expressed in today’s dollars rather than inflated future dollars. A common long-run assumption for a diversified stock portfolio is 6 to 7% after inflation.
Worked example. Contributing $500 a month for 30 years at a 7% real return, with no starting balance, grows to about $613,544 in today’s dollars. Most of that is compound growth, not the contributions themselves.
Common questions
- What return rate should I use?
- Enter a real return, one already net of inflation. A common long-run assumption for a diversified stock portfolio is 6 to 7% after inflation. Because the rate is real, the projected balance is in today’s dollars.
- Does this account for inflation?
- Yes, as long as you enter a real return. The calculator treats your rate as already net of inflation and reports the ending balance in today’s purchasing power, not inflated future dollars.
- Are contributions before or after tax?
- The calculator grows whatever you contribute and does not distinguish account type. Where the money sits, a traditional 401(k), Roth, or taxable account, changes your taxes, not the growth math itself.