$400 a month for 40 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $464,426 | $272,426 | $142,373 |
| 5% | $593,010 | $401,010 | $181,791 |
| 6% | $763,071 | $571,071 | $233,925 |
| 7% | $988,617 | $796,617 | $303,067 |
| 8% | $1,288,432 | $1,096,432 | $394,978 |
| 10% | $2,220,139 | $2,028,139 | $680,599 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $4,800 | $4,952 | $4,808 |
| 2 | $9,600 | $10,251 | $9,662 |
| 3 | $14,400 | $15,921 | $14,570 |
| 5 | $24,000 | $28,478 | $24,566 |
| 10 | $48,000 | $68,421 | $50,911 |
| 15 | $72,000 | $124,442 | $79,875 |
| 20 | $96,000 | $203,015 | $112,404 |
| 25 | $120,000 | $313,217 | $149,594 |
| 30 | $144,000 | $467,781 | $192,720 |
| 35 | $168,000 | $684,565 | $243,283 |
| 40 | $192,000 | $988,617 | $303,067 |
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 $400 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) |
|---|---|---|---|
| 20 years | $122,546 | $189,615 | $301,108 |
| 40 years | $435,566 | $865,256 | $1,723,976 |
The middle of the simulation sits below the steady 7% figure of $988,617 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $988,617 would pay in retirement
At a 4% first-year withdrawal, $988,617 pays about $39,545 a year, $3,295 a month, before tax; in today’s dollars that is about $12,123 a year. How long a balance near it lasts at each withdrawal: how long $1 million lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$4,800 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.
$400 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $400 a month for 5 years | $28,478 | $24,566 |
| $400 a month for 10 years | $68,421 | $50,911 |
| $400 a month for 15 years | $124,442 | $79,875 |
| $400 a month for 20 years | $203,015 | $112,404 |
| $400 a month for 25 years | $313,217 | $149,594 |
| $400 a month for 30 years | $467,781 | $192,720 |
| $400 a month for 35 years | $684,565 | $243,283 |
| 40 years | $988,617 | $303,067 |
Other amounts for 40 years
$50 a month: $123,577, $100 a month: $247,154, $150 a month: $370,731, $200 a month: $494,308, $250 a month: $617,886, $300 a month: $741,463, $500 a month: $1,235,771, $600 a month: $1,482,925, $750 a month: $1,853,657, $1,000 a month: $2,471,542, $1,500 a month: $3,707,313, $2,000 a month: $4,943,084, $2,500 a month: $6,178,855, $3,000 a month: $7,414,626, $5,000 a month: $12,357,710.
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.