See exactly how your money grows over time. Model contributions, compounding frequency, and inflation with an interactive chart, year-by-year schedule, and side-by-side scenario comparison — free, no account required.
Worth in today's dollars, after inflation
| Year | Contributions | Interest earned | Ending balance | In today's dollars |
|---|---|---|---|---|
| 1 | $3,600 | $862 | $14,462 | $14,041 |
| 2 | $3,600 | $1,185 | $19,247 | $18,142 |
| 3 | $3,600 | $1,531 | $24,378 | $22,309 |
| 4 | $3,600 | $1,902 | $29,880 | $26,548 |
| 5 | $3,600 | $2,299 | $35,779 | $30,864 |
| 6 | $3,600 | $2,726 | $42,105 | $35,263 |
| 7 | $3,600 | $3,183 | $48,889 | $39,751 |
| 8 | $3,600 | $3,674 | $56,162 | $44,335 |
| 9 | $3,600 | $4,199 | $63,962 | $49,021 |
| 10 | $3,600 | $4,763 | $72,325 | $53,817 |
| 11 | $3,600 | $5,368 | $81,293 | $58,728 |
| 12 | $3,600 | $6,016 | $90,909 | $63,762 |
| 13 | $3,600 | $6,711 | $101,220 | $68,926 |
| 14 | $3,600 | $7,457 | $112,277 | $74,228 |
| 15 | $3,600 | $8,256 | $124,133 | $79,676 |
| 16 | $3,600 | $9,113 | $136,846 | $85,278 |
| 17 | $3,600 | $10,032 | $150,478 | $91,042 |
| 18 | $3,600 | $11,018 | $165,095 | $96,976 |
| 19 | $3,600 | $12,074 | $180,770 | $103,090 |
| 20 | $3,600 | $13,207 | $197,577 | $109,394 |
| 21 | $3,600 | $14,422 | $215,599 | $115,895 |
| 22 | $3,600 | $15,725 | $234,924 | $122,605 |
| 23 | $3,600 | $17,122 | $255,647 | $129,534 |
| 24 | $3,600 | $18,620 | $277,867 | $136,692 |
| 25 | $3,600 | $20,226 | $301,693 | $144,090 |
Compound interest is interest earned on both your original investment and on the interest that investment has already earned. Instead of only growing by a fixed amount each year, your balance grows by a percentage of an ever-larger number — which is why the curve above bends upward instead of forming a straight line.
Time is the single biggest input in this formula, and it's the one thing you can't buy back later. Money invested in your 20s has decades to compound, so even small amounts can end up outgrowing much larger sums invested later. The comparison below shows exactly how large that gap can get.
Raising your monthly contribution doesn't just add more principal — that extra money compounds too. A contribution increase in year one is worth far more by your final year than the same increase made later, because it has more time to grow. Try adjusting the monthly contribution slider above and watch the ending balance respond.
A dollar today won't buy as much 20 or 30 years from now. The inflation toggle in this calculator discounts your projected balance back into today's purchasing power, so you can see what your future balance is actually worth — not just what the number will read.
The S&P 500 has historically returned an average of roughly 10% per year before inflation (about 7% after inflation) over long periods, though any single year can vary dramatically — including sharp losses. This is historical information only, not a guarantee, a prediction, or personalized investment advice. Past performance does not guarantee future results, and this calculator's default 7% assumption is simply a commonly cited long-run estimate for you to adjust.
Two people each invest $200/month until age 65, assuming a 7% average annual return. The only difference is when they started.
Starting at age 18
47 years invested · $112,800 contributed
$882,403
Starting at age 28
37 years invested · $88,800 contributed
$421,755
Investing 10 years earlier is worth $460,648 more at retirement — despite contributing the same amount every month.
Illustrative example assuming a constant 7% annual return, compounded monthly. Real returns vary year to year and are never guaranteed.
Plain-English articles on investing, retirement, budgeting are in the works in our Learning Center.
Jump back up to the calculator and try a scenario that matches your real plan.
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