Coast FIRE Number by Age: What You Need at 25, 30, 35, and 40

The Formula

Coast FIRE number = Full FIRE number ÷ (1 + real annual return)^(years to retirement). This is present value math applied to retirement planning. You are asking: what amount, compounded at your expected real return for the years remaining, equals your full FIRE target? The “real return” figure uses inflation-adjusted returns — so your FIRE number and your Coast FIRE number are both expressed in today’s dollars.

Assumptions Behind the Table

The numbers below assume a full FIRE target of $1.5 million (based on $60,000 annual spending at a 4% withdrawal rate), an alternative target of $1 million (based on $40,000 spending at 4%), a real annual return of 7% (historical average for a diversified equity portfolio, per NYU Stern data), and a retirement age of 65. These are illustrative. Use the Coast FIRE calculator to run your specific numbers.

Coast FIRE Numbers by Starting Age

At age 22 with 43 years to 65, Coast FIRE is $53,000 ($40k spend) or $79,000 ($60k spend). At 25 with 40 years: $67,000 or $100,000. At 30 with 35 years: $94,000 or $141,000. At 35 with 30 years: $131,000 or $197,000. At 40 with 25 years: $185,000 or $277,000. At 45 with 20 years: $258,000 or $387,000. At 50 with 15 years: $363,000 or $544,000.

The jump between 25 and 35 is instructive. A ten-year delay doubles the required Coast FIRE number — from $100,000 to $197,000 for the $60k spending target. That is the cost of waiting.

What These Numbers Mean Practically

At 25, reaching a $100,000 portfolio is achievable in 3–5 years on a median income with a 30%+ savings rate. At that point, the portfolio is mathematically self-sufficient for retirement at 65, even if you never invest another dollar. Most people do continue contributing, which means they arrive at retirement with significantly more — the Coast threshold is a floor, not a ceiling.

At 35, $197,000 takes longer to accumulate from scratch, but many people in their mid-30s already have retirement savings from earlier working years. The Coast FIRE check is worth running against your existing 401k and IRA balance before assuming you need to start from zero.

The 7% Return Assumption: What Happens If It’s Wrong

If real returns are 5%, the Coast FIRE number at age 30 (35 years to 65) for a $60k spending target rises to approximately $270,000 — nearly double the 7% figure of $141,000. If real returns are 9%, the same scenario produces approximately $74,000. This sensitivity to return assumptions is why the Coast FIRE calculator lets you adjust the real return input rather than hardcoding it.

Reaching Your Coast FIRE Number Faster

The most direct path is higher monthly contributions early in the accumulation phase. Each dollar invested at 25 has roughly 40 years to compound; each dollar invested at 45 has 20. The ratio of their eventual values is about 3.9 — meaning early dollars are worth nearly four times as much in retirement as mid-career ones.

The second lever is spending. A lower expected retirement spending level reduces the full FIRE target, which reduces the Coast FIRE number by the same proportion. Use the Coast FIRE calculator to model your specific age, target, and return assumption.