Your Coast FIRE Number at 40: How Much You Need Saved to Stop Worrying
What "Coast" Actually Means
Coast FIRE is the point where your invested savings are big enough that, without adding another dollar, they will grow into a full retirement nest egg by your target age. You still work to cover today's bills, but you no longer have to save for retirement. You are coasting.
Age 40 is a popular checkpoint because it leaves about 25 years of compounding before a traditional retirement at 65. That runway is what makes the math work.
The Coast FIRE Formula
Coast number = Retirement target ÷ (1 + return rate) ^ years until retirement
Your retirement target is usually 25× your expected yearly spending (the 4% rule). Your return rate should be a real return, meaning after inflation, so the result is in today's dollars.
Example: $60,000 a Year in Retirement
- Retirement target: $60,000 × 25 = $1,500,000
- Years from 40 to 65: 25
| Real return | Growth multiple over 25 years | Coast number at 40 | |---|---|---| | 6% | 4.29× | ~$350,000 | | 7% | 5.43× | ~$276,000 | | 9% | 8.62× | ~$174,000 |
The spread is big. That's why we model several return rates instead of trusting one optimistic number.
Coast Number at 40 by Spending Level (7% real return)
| Yearly retirement spending | Retirement target | Coast number at 40 | |---|---|---| | $40,000 | $1,000,000 | ~$184,000 | | $60,000 | $1,500,000 | ~$276,000 | | $80,000 | $2,000,000 | ~$368,000 | | $100,000 | $2,500,000 | ~$461,000 |
Have less than this at 40? That's normal. It means you keep contributing for a few more years, and every year of contributions shrinks the gap.
Why 40 Is the Make-or-Break Decade
Each year you wait, the coast number goes up because there's less time to compound. Using the $1.5M target at 7%:
- Coast at 35 (30 years): ~$197,000
- Coast at 40 (25 years): ~$276,000
- Coast at 45 (20 years): ~$388,000
- Coast at 50 (15 years): ~$544,000
Moving the date back five years adds roughly 40% to the number you need. The best time to build your base is your 20s and 30s. See compound interest explained for why.
What Coast FIRE Does Not Mean
- It's not retirement. You still need income to cover living costs until 65.
- It's not guaranteed. Market returns are uneven. A bad decade near your coast date can push you behind, so many people keep a small contribution going as a buffer.
- It's not set-and-forget on spending. If your retirement lifestyle grows (see lifestyle creep), your target grows too.
How to Get There Faster
- Max tax-advantaged accounts first. 401(k), IRA, TFSA, RRSP, whatever your country offers.
- Use low-cost index funds. Fees eat straight into your growth multiple. See index funds vs ETFs.
- Automate contributions so saving happens before spending.
- Pay off high-interest debt. A 22% credit card cancels out a 7% portfolio. Try the debt payoff calculator.
Find Your Own Coast Number
Plug your age, savings and target spending into the FIRE calculator or the retirement calculator to see when you cross the coast line. Then build a plan to get there in the FutureYou budget planner.
This article is for education only and isn't financial advice. Returns are not guaranteed.