Early Start — Teen Investor (18 to 65)
The power of time: a 18-year-old investing just $100 a month at 8% until 65. A pre-filled compound interest calculator scenario.
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Your inputs
Results
Future value
$621,238
Projected balance at the end of the term
Total principal invested
$56,400
Total interest earned
$564,838
Interest is 1001% of the final value
Avg. annual growth (CAGR)
5.2%
Interest vs. principal
1001%
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Growth over time
Year-by-year breakdown
| Year | Balance | Principal | Interest |
|---|---|---|---|
| 1 | $1,245 | $1,200 | $45 |
| 2 | $2,593 | $2,400 | $193 |
| 3 | $4,054 | $3,600 | $454 |
| 4 | $5,635 | $4,800 | $835 |
| 5 | $7,348 | $6,000 | $1,348 |
| 6 | $9,203 | $7,200 | $2,003 |
| 7 | $11,211 | $8,400 | $2,811 |
| 8 | $13,387 | $9,600 | $3,787 |
| 9 | $15,743 | $10,800 | $4,943 |
| 10 | $18,295 | $12,000 | $6,295 |
| 11 | $21,058 | $13,200 | $7,858 |
| 12 | $24,051 | $14,400 | $9,651 |
| 13 | $27,292 | $15,600 | $11,692 |
| 14 | $30,802 | $16,800 | $14,002 |
| 15 | $34,604 | $18,000 | $16,604 |
| 16 | $38,721 | $19,200 | $19,521 |
| 17 | $43,180 | $20,400 | $22,780 |
| 18 | $48,009 | $21,600 | $26,409 |
| 19 | $53,238 | $22,800 | $30,438 |
| 20 | $58,902 | $24,000 | $34,902 |
| 21 | $65,036 | $25,200 | $39,836 |
| 22 | $71,679 | $26,400 | $45,279 |
| 23 | $78,873 | $27,600 | $51,273 |
| 24 | $86,665 | $28,800 | $57,865 |
| 25 | $95,103 | $30,000 | $65,103 |
| 26 | $104,241 | $31,200 | $73,041 |
| 27 | $114,138 | $32,400 | $81,738 |
| 28 | $124,856 | $33,600 | $91,256 |
| 29 | $136,464 | $34,800 | $101,664 |
| 30 | $149,036 | $36,000 | $113,036 |
| 31 | $162,651 | $37,200 | $125,451 |
| 32 | $177,396 | $38,400 | $138,996 |
| 33 | $193,365 | $39,600 | $153,765 |
| 34 | $210,659 | $40,800 | $169,859 |
| 35 | $229,388 | $42,000 | $187,388 |
| 36 | $249,672 | $43,200 | $206,472 |
| 37 | $271,640 | $44,400 | $227,240 |
| 38 | $295,431 | $45,600 | $249,831 |
| 39 | $321,197 | $46,800 | $274,397 |
| 40 | $349,101 | $48,000 | $301,101 |
| 41 | $379,321 | $49,200 | $330,121 |
| 42 | $412,049 | $50,400 | $361,649 |
| 43 | $447,494 | $51,600 | $395,894 |
| 44 | $485,881 | $52,800 | $433,081 |
| 45 | $527,454 | $54,000 | $473,454 |
| 46 | $572,477 | $55,200 | $517,277 |
| 47 | $621,238 | $56,400 | $564,838 |
Features
- Year-by-year growth table
- Future value, principal & interest breakdown
- Compound interest formula explained
- Shareable result card
Scenario Benchmark
Key figures for Early Start — Teen Investor (18 to 65).
Future value
$621,238
Total principal invested
$56,400
Total interest earned
$564,838
Interest vs. principal
1001%
Avg. annual growth (CAGR)
5.2%
years
47
Frequently asked questions
How the maths works
Compound interest means you earn returns on your returns. The more often interest compounds, the faster the balance grows.
- 1Start with your initial principal P.
- 2Each compounding period, the balance earns the periodic rate r/n, then the periodic deposit is added.
- 3Repeat for n compounding periods per year across all t years.
- 4The final balance A is your future value; subtract total deposits to find the interest earned.
Figures are nominal and exclude taxes, fees and inflation. They are illustrative, not financial advice.
Everything you need to know
What is compound interest?
Compound interest is the process where the interest you earn is reinvested, so future interest is calculated on a larger balance.
Over long horizons this snowball effect dwarfs the impact of your original deposit.
How often should interest compound?
More frequent compounding (monthly vs. annually) produces slightly more growth because interest starts earning sooner.
Our calculator defaults to monthly compounding, the most common schedule for brokerage and retirement accounts.
- Annual (n=1)
- Semi-annual (n=2)
- Quarterly (n=4)
- Monthly (n=12)
Making the most of compounding
Start early — time is the single biggest lever on the final balance.
Contribute consistently and reinvest dividends to maximize the snowball.
Even modest monthly deposits compound into large sums over decades.
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