How much will $300 a month be worth in 20 years?

Investing $300 a month for 20 years means paying in $72,000 in total. At a hypothetical 7% annual return it would grow to $152,261: $72,000 from your contributions and $80,261 from investment growth. At 4% the balance would be $109,153 ($37,153 of growth), and at 10% it would be $215,478 ($143,478 of growth).

At 4% a year

$109,153

$37,153 of that is growth

At 7% a year

$152,261

$80,261 of that is growth

At 10% a year

$215,478

$143,478 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.

$300 a month for 20 years at different rates of return

Annual return	Final balance	Total contributed	Interest earned
1%	$79,631	$72,000	$7,631
2%	$88,269	$72,000	$16,269
3%	$98,056	$72,000	$26,056
4%	$109,153	$72,000	$37,153
5%	$121,741	$72,000	$49,741
6%	$136,032	$72,000	$64,032
7%	$152,261	$72,000	$80,261
8%	$170,700	$72,000	$98,700
9%	$191,656	$72,000	$119,656
10%	$215,478	$72,000	$143,478
11%	$242,563	$72,000	$170,563
12%	$273,363	$72,000	$201,363

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 $72,000 in every row; only the growth changes, from $7,631 at 1% to $201,363 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 20 years

$152,261

52.7% of that is interest. Your balance is 2.11 times what you put in.

Total contributions

$72,000

Interest earned

$80,261

Growth by year

Contributions
Interest

Year-by-year breakdown

Year	Contributions	Interest	Balance
1	$3,600	$114	$3,714
2	$7,200	$488	$7,688
3	$10,800	$1,140	$11,940
4	$14,400	$2,090	$16,490
5	$18,000	$3,359	$21,359
6	$21,600	$4,968	$26,568
7	$25,200	$6,942	$32,142
8	$28,800	$9,306	$38,106
9	$32,400	$12,087	$44,487
10	$36,000	$15,316	$51,316
11	$39,600	$19,022	$58,622
12	$43,200	$23,239	$66,439
13	$46,800	$28,004	$74,804
14	$50,400	$33,355	$83,755
15	$54,000	$39,331	$93,331
16	$57,600	$45,979	$103,579
17	$61,200	$53,343	$114,543
18	$64,800	$61,475	$126,275
19	$68,400	$70,429	$138,829
20	$72,000	$80,261	$152,261

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 20 growth makes up 53% 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 20-year period ends.

In year 20 alone, the balance earns $9,832 at 7%. That is more than the $3,600 you add that year, and compares with $114 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 $300 a month for 20 years, which ends at $152,261.

Change	Final balance	Difference
Keep contributing for 5 more years (25 years in total)	$234,913	+$82,652
Start 5 years later (contribute for 15 years)	$93,331	−$58,929
Contribute $400 a month instead of $300	$203,015	+$50,754
Start with $10,000 already invested	$190,958	+$38,697
Contribute at the start of each month instead of the end	$153,122	+$861
Earn 6% a year instead of 7%	$136,032	−$16,229

Starting 5 years later means paying in $18,000 less, but the final balance is $58,929 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 $16,229 less after 20 years, which is roughly what a 1% annual fee would cost.

Working backwards: to reach $250,000 in 20 years at 7%, starting from zero, you would need to invest about $493 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 $300 a month continues for as long as it takes. Years in bold fall within this page's 20-year period.

Balance reaches	At 4%	At 7%	At 10%
$10,000	Year 3	Year 3	Year 3
$25,000	Year 7	Year 6	Year 6
$50,000	Year 12	Year 10	Year 9
$100,000	Year 19	Year 16	Year 14
$250,000	Year 34	Year 26	Year 22

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 $300 added at the end of each month for 240 months (20 × 12), the contributions grow to:

Balance = 300 × [1.005654²⁴⁰ − 1] ÷ 0.005654 ≈ $152,261

The rates shown here are rounded; the result uses full precision. Of that balance, 300 × 240 = $72,000 is your contributions and the remaining $80,261 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 $300 a month earn in 20 years?

It depends on the rate of return. At a constant 7% a year, $300 a month for 20 years earns $80,261 on top of $72,000 in contributions, for a balance of $152,261. At 4% the growth is $37,153, and at 10% it is $143,478. These rates are examples, not predictions.

How long does it take to reach $250,000 investing $300 a month?

With a constant 7% annual return and no starting balance, the balance passes $250,000 during year 26. For comparison, at 10% it takes until year 22, and at 4% it takes until year 34.

How much do I need to invest each month to have $250,000 in 20 years?

At a constant 7% annual return you would need about $493 a month for 20 years, starting from zero. At 4% you would need about $687 a month, and at 10% about $348 a month.

$300 a month over other periods

Other monthly amounts for 20 years

A single lump sum for 20 years

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