Coast FIRE Calculator

Coast FIRE is the moment when your current invested balance is sufficient to grow into your full FIRE number by your target retirement age without any additional contributions. Once you hit Coast FIRE, you only need to cover your current living expenses — no more retirement saving. Coined by The Fioneers and JL Collins as a flexible alternative to full FIRE.

Coast vs Lean vs Fat FIRE

Lean FIRE: total invested balance covers minimum spend (~$25k-40k/year). Fat FIRE: total invested balance covers luxury spend ($100k+/year). Coast FIRE: current balance is enough for any spend level by retirement age — you just need to wait. Barista FIRE: covers spend if you keep a part-time job for health insurance and supplemental income. Coast is the most achievable for high-earning 30-somethings who frontloaded retirement savings in their 20s.

How the Calculation Works

Coast FIRE number = (Annual Spend ÷ Safe Withdrawal Rate) ÷ (1 + Real Return)^Years to Retirement. Example: $60k/year spend at 4% SWR = $1.5M FIRE number. At 7% real return over 33 years (age 32 to 65), the present value is $1.5M ÷ 1.07^33 = $164k. Hit $164k by age 32, stop saving, and you mathematically reach $1.5M by 65.

Risks and Reality Checks

(1) Sequence-of-returns risk: a 30% market crash in your 60s can derail the plan — stress test with 5% returns instead of 7%. (2) Inflation: 3% inflation over 33 years requires $60k to become $159k of spend — use REAL returns (7%) not nominal (10%). (3) Health insurance: if Coast means stopping work entirely, US healthcare costs $1,000-2,000/month without employer coverage. (4) Lifestyle creep: spending tends to grow with income; lock in current spend before declaring Coast.

Last updated May 2026. Sources: The Fioneers — Coast FIRE Origin, Trinity Study — 4% Rule.