$400 a month for 10 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $58,678 | $10,678 | $43,662 |
| 5% | $61,745 | $13,745 | $45,944 |
| 6% | $64,989 | $16,989 | $48,358 |
| 7% | $68,421 | $20,421 | $50,911 |
| 8% | $72,050 | $24,050 | $53,612 |
| 10% | $79,946 | $31,946 | $59,487 |
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 |
| 4 | $19,200 | $21,987 | $19,535 |
| 5 | $24,000 | $28,478 | $24,566 |
| 6 | $28,800 | $35,424 | $29,667 |
| 7 | $33,600 | $42,856 | $34,846 |
| 8 | $38,400 | $50,808 | $40,108 |
| 9 | $43,200 | $59,316 | $45,461 |
| 10 | $48,000 | $68,421 | $50,911 |
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) |
|---|---|---|---|
| 5 years | $23,232 | $28,060 | $34,160 |
| 10 years | $50,415 | $66,204 | $87,518 |
The middle of the simulation sits below the steady 7% figure of $68,421 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $68,421 would pay in retirement
At a 4% first-year withdrawal, $68,421 pays about $2,737 a year, $228 a month, before tax; in today’s dollars that is about $2,036 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.
$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 |
| 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 |
| $400 a month for 40 years | $988,617 | $303,067 |
Other amounts for 10 years
$50 a month: $8,553, $100 a month: $17,105, $150 a month: $25,658, $200 a month: $34,210, $250 a month: $42,763, $300 a month: $51,316, $500 a month: $85,526, $600 a month: $102,631, $750 a month: $128,289, $1,000 a month: $171,052, $1,500 a month: $256,578, $2,000 a month: $342,103, $2,500 a month: $427,629, $3,000 a month: $513,155, $5,000 a month: $855,259.
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.