How much will $100 a month be worth in 30 years?

Investing $100 a month for 30 years means paying in $36,000 in total. At a hypothetical 7% annual return it would grow to $116,945: $36,000 from your contributions and $80,945 from investment growth. At 4% the balance would be $68,527 ($32,527 of growth), and at 10% it would be $206,284 ($170,284 of growth).

At 4% a year

$68,527

$32,527 of that is growth

At 7% a year

$116,945

$80,945 of that is growth

At 10% a year

$206,284

$170,284 of that is growth

4%, 7% and 10% are example rates, not forecasts. Real returns change from year to year and are never guaranteed, and these figures leave out fees, taxes and inflation.

$100 a month for 30 years at different rates of return

Annual return	Final balance	Total contributed	Interest earned
1%	$41,933	$36,000	$5,933
2%	$49,126	$36,000	$13,126
3%	$57,871	$36,000	$21,871
4%	$68,527	$36,000	$32,527
5%	$81,538	$36,000	$45,538
6%	$97,451	$36,000	$61,451
7%	$116,945	$36,000	$80,945
8%	$140,855	$36,000	$104,855
9%	$170,211	$36,000	$134,211
10%	$206,284	$36,000	$170,284
11%	$250,639	$36,000	$214,639
12%	$305,201	$36,000	$269,201

Assumes no starting balance, a contribution at the end of every month, and a constant rate compounded once a year (an effective annual rate). You pay in $36,000 in every row; only the growth changes, from $5,933 at 1% to $269,201 at 12%.

Try your own numbers

The calculator starts with this example at 7%. Change the amount, rate or time period, add a starting balance, or switch the compounding, and the result updates as you type.

Balance after 30 years

$116,945

69.2% of that is interest. Your balance is 3.25 times what you put in.

Total contributions

$36,000

Interest earned

$80,945

Growth by year

Contributions
Interest

Year-by-year breakdown

Year	Contributions	Interest	Balance
1	$1,200	$38	$1,238
2	$2,400	$163	$2,563
3	$3,600	$380	$3,980
4	$4,800	$697	$5,497
5	$6,000	$1,120	$7,120
6	$7,200	$1,656	$8,856
7	$8,400	$2,314	$10,714
8	$9,600	$3,102	$12,702
9	$10,800	$4,029	$14,829
10	$12,000	$5,105	$17,105
11	$13,200	$6,341	$19,541
12	$14,400	$7,746	$22,146
13	$15,600	$9,335	$24,935
14	$16,800	$11,118	$27,918
15	$18,000	$13,110	$31,110
16	$19,200	$15,326	$34,526
17	$20,400	$17,781	$38,181
18	$21,600	$20,492	$42,092
19	$22,800	$23,476	$46,276
20	$24,000	$26,754	$50,754
21	$25,200	$30,344	$55,544
22	$26,400	$34,271	$60,671
23	$27,600	$38,556	$66,156
24	$28,800	$43,224	$72,024
25	$30,000	$48,304	$78,304
26	$31,200	$53,824	$85,024
27	$32,400	$59,813	$92,213
28	$33,600	$66,306	$99,906
29	$34,800	$73,338	$108,138
30	$36,000	$80,945	$116,945

How much is your money and how much is growth?

At 7%, most of the balance is money you paid in for the first 18 years. During year 19, total growth passes total contributions, and by the end of year 30 growth makes up 69% of the balance. The rate matters a lot here: growth overtakes contributions in year 14 at 10%, while at 4% it would take until year 33, after this 30-year period ends.

In year 30 alone, the balance earns $7,608 at 7%. That is more than the $1,200 you add that year, and compares with $38 of growth in year 1.

What if you change the plan?

Each row changes one thing and keeps everything else the same, at the 7% example rate. The comparison is with $100 a month for 30 years, which ends at $116,945.

Change	Final balance	Difference
Keep contributing for 5 more years (35 years in total)	$171,141	+$54,196
Start 5 years later (contribute for 25 years)	$78,304	−$38,641
Contribute $200 a month instead of $100	$233,891	+$116,945
Start with $10,000 already invested	$193,068	+$76,123
Contribute at the start of each month instead of the end	$117,606	+$661
Earn 6% a year instead of 7%	$97,451	−$19,494

Starting 5 years later means paying in $6,000 less, but the final balance is $38,641 lower. The gap is bigger than the missing contributions because the earliest payments are the ones with the longest time to grow. A return that is one point lower leaves you with $19,494 less after 30 years, which is roughly what a 1% annual fee would cost.

Working backwards: to reach $250,000 in 30 years at 7%, starting from zero, you would need to invest about $214 a month.

When would the balance reach $250,000?

The table shows the year in which the balance first reaches each amount, assuming the same $100 a month continues for as long as it takes. Years in bold fall within this page's 30-year period.

Balance reaches	At 4%	At 7%	At 10%
$10,000	Year 8	Year 7	Year 7
$25,000	Year 16	Year 14	Year 12
$50,000	Year 25	Year 20	Year 17
$100,000	Year 38	Year 29	Year 24
$250,000	Over 50 years	Year 41	Year 32

How this is calculated

The rate is treated as an effective annual rate, so the balance grows by exactly 7% over a full year. The monthly rate that compounds to 7% a year is:

Monthly rate = (1 + 0.07)^1/12 − 1 = 0.5654%

With $100 added at the end of each month for 360 months (30 × 12), the contributions grow to:

Balance = 100 × [1.005654³⁶⁰ − 1] ÷ 0.005654 ≈ $116,945

The rates shown here are rounded; the result uses full precision. Of that balance, 100 × 360 = $36,000 is your contributions and the remaining $80,945 is growth. Every other row in the rate table uses the same formula with a different annual rate. The compound interest calculator page explains the formulas in more detail.

Frequently asked questions

How much interest will $100 a month earn in 30 years?

It depends on the rate of return. At a constant 7% a year, $100 a month for 30 years earns $80,945 on top of $36,000 in contributions, for a balance of $116,945. At 4% the growth is $32,527, and at 10% it is $170,284. These rates are examples, not predictions.

How long does it take to reach $250,000 investing $100 a month?

With a constant 7% annual return and no starting balance, the balance passes $250,000 during year 41. For comparison, at 10% it takes until year 32, and at 4% it would not get there within 50 years.

How much do I need to invest each month to have $250,000 in 30 years?

At a constant 7% annual return you would need about $214 a month for 30 years, starting from zero. At 4% you would need about $365 a month, and at 10% about $121 a month.

$100 a month over other periods

Other monthly amounts for 30 years

A single lump sum for 30 years

See all compound interest examples in one table, or start from scratch with the compound interest calculator.