$100 a month for 35 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $89,992 | $47,992 | $31,982 |
| 5% | $110,846 | $68,846 | $39,393 |
| 6% | $137,360 | $95,360 | $48,816 |
| 7% | $171,141 | $129,141 | $60,821 |
| 8% | $214,257 | $172,257 | $76,143 |
| 10% | $339,879 | $297,879 | $120,787 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $1,200 | $1,238 | $1,202 |
| 2 | $2,400 | $2,563 | $2,416 |
| 3 | $3,600 | $3,980 | $3,642 |
| 5 | $6,000 | $7,120 | $6,141 |
| 10 | $12,000 | $17,105 | $12,728 |
| 15 | $18,000 | $31,110 | $19,969 |
| 20 | $24,000 | $50,754 | $28,101 |
| 25 | $30,000 | $78,304 | $37,399 |
| 30 | $36,000 | $116,945 | $48,180 |
| 35 | $42,000 | $171,141 | $60,821 |
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 $100 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) |
|---|---|---|---|
| 18 years | $26,435 | $39,616 | $61,175 |
| 35 years | $84,312 | $154,862 | $296,216 |
The middle of the simulation sits below the steady 7% figure of $171,141 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $171,141 would pay in retirement
At a 4% first-year withdrawal, $171,141 pays about $6,846 a year, $570 a month, before tax; in today’s dollars that is about $2,433 a year. How long a balance near it lasts at each withdrawal: how long $150,000 lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$1,200 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.
$100 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $100 a month for 5 years | $7,120 | $6,141 |
| $100 a month for 10 years | $17,105 | $12,728 |
| $100 a month for 15 years | $31,110 | $19,969 |
| $100 a month for 20 years | $50,754 | $28,101 |
| $100 a month for 25 years | $78,304 | $37,399 |
| $100 a month for 30 years | $116,945 | $48,180 |
| 35 years | $171,141 | $60,821 |
| $100 a month for 40 years | $247,154 | $75,767 |
Other amounts for 35 years
$50 a month: $85,571, $150 a month: $256,712, $200 a month: $342,283, $250 a month: $427,853, $300 a month: $513,424, $400 a month: $684,565, $500 a month: $855,707, $600 a month: $1,026,848, $750 a month: $1,283,560, $1,000 a month: $1,711,414, $1,500 a month: $2,567,120, $2,000 a month: $3,422,827, $2,500 a month: $4,278,534, $3,000 a month: $5,134,241, $5,000 a month: $8,557,068.
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.