Investment Growth Calculator
See how compound interest grows your investments over time
Investment Inputs
Initial investment amount
Amount added each month
Expected annual return (7% is typical for stocks)
Investment time horizon
Average annual inflation to adjust for purchasing power
Investment Summary
| Year | Starting Balance | Contributions | Interest Earned | Ending Balance |
|---|---|---|---|---|
| 1 | $0.00 | $6,000.00 | $196.29 | $6,196.29 |
| 2 | $6,196.29 | $6,000.00 | $644.22 | $12,840.52 |
| 3 | $12,840.52 | $6,000.00 | $1,124.53 | $19,965.05 |
| 4 | $19,965.05 | $6,000.00 | $1,639.57 | $27,604.62 |
| 5 | $27,604.62 | $6,000.00 | $2,191.83 | $35,796.45 |
| 6 | $35,796.45 | $6,000.00 | $2,784.02 | $44,580.47 |
| 7 | $44,580.47 | $6,000.00 | $3,419.02 | $53,999.49 |
| 8 | $53,999.49 | $6,000.00 | $4,099.92 | $64,099.41 |
| 9 | $64,099.41 | $6,000.00 | $4,830.04 | $74,929.45 |
| 10 | $74,929.45 | $6,000.00 | $5,612.95 | $86,542.40 |
| 11 | $86,542.40 | $6,000.00 | $6,452.45 | $98,994.85 |
| 12 | $98,994.85 | $6,000.00 | $7,352.64 | $112,347.49 |
| 13 | $112,347.49 | $6,000.00 | $8,317.90 | $126,665.39 |
| 14 | $126,665.39 | $6,000.00 | $9,352.94 | $142,018.34 |
| 15 | $142,018.34 | $6,000.00 | $10,462.81 | $158,481.15 |
| 16 | $158,481.15 | $6,000.00 | $11,652.91 | $176,134.06 |
| 17 | $176,134.06 | $6,000.00 | $12,929.04 | $195,063.09 |
| 18 | $195,063.09 | $6,000.00 | $14,297.42 | $215,360.51 |
| 19 | $215,360.51 | $6,000.00 | $15,764.72 | $237,125.23 |
| 20 | $237,125.23 | $6,000.00 | $17,338.10 | $260,463.33 |
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Get Started FreeFrequently Asked Questions
What is compound interest?
Compound interest is interest earned on both your original investment and on previously earned interest. Over time, this creates exponential growth — your money earns money, which earns more money. It's often called the 'eighth wonder of the world.'
How much should I invest monthly?
A common guideline is to invest 15-20% of your gross income for retirement. However, any amount helps — even $100/month invested at 7% annual return grows to over $120,000 in 20 years thanks to compound interest.
What is a realistic annual return rate?
The S&P 500 has historically returned about 10% annually before inflation (roughly 7% after inflation). A diversified portfolio of stocks and bonds might return 6-8% after inflation. Use 7% as a reasonable long-term estimate for a stock-heavy portfolio.
Why should I adjust for inflation?
Inflation reduces the purchasing power of your money over time. $1 million in 30 years won't buy as much as $1 million today. The inflation-adjusted (real) return shows what your future balance is worth in today's dollars, giving you a more realistic picture.
When should I start investing?
As early as possible. Thanks to compound interest, someone who invests $200/month starting at age 25 will have significantly more at retirement than someone who invests $400/month starting at age 35 — even though the late starter contributes more total money.
What is the difference between nominal and real returns?
Nominal return is the raw percentage your investments earn. Real return is the nominal return minus inflation. If your investments earn 10% and inflation is 3%, your real return is roughly 7%. The calculator above lets you see both.