$150 a month for 20 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $54,576 | $18,576 | $30,218 |
| 5% | $60,871 | $24,871 | $33,703 |
| 6% | $68,016 | $32,016 | $37,659 |
| 7% | $76,130 | $40,130 | $42,152 |
| 8% | $85,350 | $49,350 | $47,256 |
| 10% | $107,739 | $71,739 | $59,652 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $1,800 | $1,857 | $1,803 |
| 2 | $3,600 | $3,844 | $3,623 |
| 3 | $5,400 | $5,970 | $5,464 |
| 4 | $7,200 | $8,245 | $7,326 |
| 5 | $9,000 | $10,679 | $9,212 |
| 6 | $10,800 | $13,284 | $11,125 |
| 7 | $12,600 | $16,071 | $13,067 |
| 8 | $14,400 | $19,053 | $15,041 |
| 9 | $16,200 | $22,244 | $17,048 |
| 10 | $18,000 | $25,658 | $19,092 |
| 11 | $19,800 | $29,311 | $21,175 |
| 12 | $21,600 | $33,220 | $23,300 |
| 13 | $23,400 | $37,402 | $25,469 |
| 14 | $25,200 | $41,877 | $27,686 |
| 15 | $27,000 | $46,666 | $29,953 |
| 16 | $28,800 | $51,789 | $32,273 |
| 17 | $30,600 | $57,272 | $34,650 |
| 18 | $32,400 | $63,138 | $37,087 |
| 19 | $34,200 | $69,414 | $39,586 |
| 20 | $36,000 | $76,130 | $42,152 |
The range in 1,000 simulated markets
A 7% average does not arrive as 7% every year. In 1,000 simulated sequences of returns averaging 7% with 12% volatility, this is where $150 a month ended up: 1 in 10 markets finished below the first figure, half below the middle one, and 1 in 10 above the last.
| After | Weak (1 in 10 lower) | Middle | Strong (1 in 10 higher) |
|---|---|---|---|
| 10 years | $18,905 | $24,827 | $32,819 |
| 20 years | $45,955 | $71,106 | $112,915 |
The middle of the simulation sits below the steady 7% figure of $76,130 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $76,130 would pay in retirement
At a 4% first-year withdrawal, $76,130 pays about $3,045 a year, $254 a month, before tax; in today’s dollars that is about $1,686 a year. How long a balance near it lasts at each withdrawal: how long $100,000 lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$1,800 a year fits in an IRA, whose 2026 limit is $7,500 under 50. See contribution limits, the 401(k) calculator and the Roth IRA calculator.
$150 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $150 a month for 5 years | $10,679 | $9,212 |
| $150 a month for 10 years | $25,658 | $19,092 |
| $150 a month for 15 years | $46,666 | $29,953 |
| 20 years | $76,130 | $42,152 |
| $150 a month for 25 years | $117,456 | $56,098 |
| $150 a month for 30 years | $175,418 | $72,270 |
| $150 a month for 35 years | $256,712 | $91,231 |
| $150 a month for 40 years | $370,731 | $113,650 |
Other amounts for 20 years
$50 a month: $25,377, $100 a month: $50,754, $200 a month: $101,507, $250 a month: $126,884, $300 a month: $152,261, $400 a month: $203,015, $500 a month: $253,768, $600 a month: $304,522, $750 a month: $380,652, $1,000 a month: $507,536, $1,500 a month: $761,305, $2,000 a month: $1,015,073, $2,500 a month: $1,268,841, $3,000 a month: $1,522,609, $5,000 a month: $2,537,682.
How it is worked out
Monthly amounts are deposited at the end of each month and compounded monthly at the rate that equals the annual return; lump sums compound once a year. The headline return is 7% a year, the Trinity-style average the site’s retirement pages use; stock-heavy portfolios have averaged more over long periods and bond-heavy ones less, which is why every page shows 4% to 10%. Today’s dollars divide by 3% inflation a year. The range comes from 1,000 simulated sequences of yearly returns averaging 7% with 12% volatility, with each year’s deposits added through the year. Fees and taxes are not taken out. More on the methodology page.