Compound Growth in Investing — Investing

Step 1

The lesson

You learned compound interest in Money Fundamentals. Investing works the same way: when returns are reinvested, future returns are earned on a bigger base.

Many funds let you automatically reinvest dividends, buying more shares instead of paying you cash. Over decades, reinvested dividends have made up a meaningful part of stock market returns.

Key term

Dollar-cost averaging

Investing a set amount on a regular schedule, like $50 every month, no matter what the market is doing. You buy more shares when prices are low and fewer when they're high, and you never have to guess the "right" time.

The biggest lever is still time. Starting ten years earlier can matter more than investing twice as much later.

Step 2

See it

$100 a month until 65, at a hypothetical 7%Hypothetical example

Step 3

Real-world example

The ten-year head start

Three people invest $100 a month until age 65, at a hypothetical 7% a year.

Starting at 16: about $506,922 (they put in $58,800).
Starting at 26: about $243,630 (they put in $46,800).
Starting at 36: about $112,617 (they put in $34,800).

The person who started at 16 put in only $12,000 more than the person who started at 26 — but ends with about $263,292 more. Those early dollars had the longest time to compound.

Step 4

Try it: your own head start

Try $100 a month for 49 years (starting at 16), then for 39 years (starting at 26).

Your numbers

Starting amount

Monthly contribution

Time

Hypothetical annual return

Real returns vary year to year and can be negative.

Results

Hypothetical balance after 49 years

$506,922

Compounded monthly at a constant 7% a year

You contributed

$58,800

Hypothetical growth

$448,122

Growth share

88%

of the final balance

Show year-by-year table

Hypothetical balance by year
Year	Contributed	Growth	Balance
1	$1,200	$39	$1,239
2	$2,400	$168	$2,568
3	$3,600	$393	$3,993
4	$4,800	$721	$5,521
5	$6,000	$1,159	$7,159
6	$7,200	$1,716	$8,916
7	$8,400	$2,400	$10,800
8	$9,600	$3,220	$12,820
9	$10,800	$4,186	$14,986
10	$12,000	$5,308	$17,308
11	$13,200	$6,599	$19,799
12	$14,400	$8,069	$22,469
13	$15,600	$9,733	$25,333
14	$16,800	$11,604	$28,404
15	$18,000	$13,696	$31,696
16	$19,200	$16,027	$35,227
17	$20,400	$18,613	$39,013
18	$21,600	$21,472	$43,072
19	$22,800	$24,625	$47,425
20	$24,000	$28,093	$52,093
21	$25,200	$31,898	$57,098
22	$26,400	$36,065	$62,465
23	$27,600	$40,619	$68,219
24	$28,800	$45,590	$74,390
25	$30,000	$51,007	$81,007
26	$31,200	$56,902	$88,102
27	$32,400	$63,311	$95,711
28	$33,600	$70,269	$103,869
29	$34,800	$77,817	$112,617
30	$36,000	$85,997	$121,997
31	$37,200	$94,856	$132,056
32	$38,400	$104,441	$142,841
33	$39,600	$114,806	$154,406
34	$40,800	$126,008	$166,808
35	$42,000	$138,105	$180,105
36	$43,200	$151,165	$194,365
37	$44,400	$165,254	$209,654
38	$45,600	$180,450	$226,050
39	$46,800	$196,830	$243,630
40	$48,000	$214,481	$262,481
41	$49,200	$233,495	$282,695
42	$50,400	$253,971	$304,371
43	$51,600	$276,013	$327,613
44	$52,800	$299,735	$352,535
45	$54,000	$325,259	$379,259
46	$55,200	$352,715	$407,915
47	$56,400	$382,243	$438,643
48	$57,600	$413,992	$471,592
49	$58,800	$448,122	$506,922

Educational calculator, not financial advice. Results are hypothetical estimates based on the numbers you enter.

Step 5

Knowledge check

Answer each question, then check your answer to see the explanation. Retake it as many times as you like.

Question 1 of 3

Step 6

Summary

Investment returns compound when they're reinvested. Dollar-cost averaging builds the habit without timing the market. Time is the biggest lever: early, regular investing can outgrow larger contributions made later. All examples are hypothetical — real returns vary.

Step 7

What you should remember

Reinvested returns compound.
Dollar-cost averaging = invest the same amount on a schedule.
Starting early is the most powerful move.
Real returns are uneven and never guaranteed.