How do I calculate my Coast FIRE number?
Your Coast FIRE number is your target retirement portfolio divided by (1 + growth rate) raised to the power of years until retirement. For example, if you need $1,000,000 at 65 and have 30 years at 7% real returns, your Coast FIRE number is approximately $131,367 today.
Formula
Coast FIRE Number = FIRE Number / (1 + annual real return rate) ^ years until retirement
Example
Target retirement portfolio: $1,250,000 at age 65. Current age: 35. Years until retirement: 30. Assumed real return: 7%. Coast FIRE Number = $1,250,000 / (1.07)^30 = $1,250,000 / 7.612 = approximately $164,209. If you already have $164,209 invested today, you can stop contributing and still retire on schedule.
How it works in detail
Coast FIRE is the point at which your existing investments will compound to your full FIRE number by retirement age — without any additional contributions. The calculation discounts your FIRE number back to today's dollars using an assumed real (inflation-adjusted) rate of return. The standard assumption is 5–7% real annual growth, consistent with long-run US equity market averages cited in research by Vanguard and Morningstar. Using 7% is more optimistic; 5% is more conservative and accounts for a diversified portfolio with bond exposure. Once you've hit your Coast FIRE number, you only need to earn enough to cover current living expenses — you can stop saving for retirement entirely. This makes Coast FIRE especially attractive for people who want to downshift careers, take lower-paying meaningful work, or reduce work hours without derailing retirement. Key caveats: the calculation is sensitive to both your assumed growth rate and your target retirement age. A 1% change in assumed returns can shift your Coast number by 20–30%. It also does not account for Social Security income, which would reduce your required portfolio size and therefore lower your Coast number meaningfully for most people.
Use Rightmont's Coast FIRE calculator to find your exact Coast number based on your age, current savings, and retirement target.
Open Free Calculator →Related Questions
What is Coast FIRE and how much do I need?
Coast FIRE is the invested balance today that will compound to your FIRE number by retirement age without any additional contributions. If your FIRE number is $1.5M and you're 30 with a 7% real return, you need $194,000 today to coast — meaning you only need to earn enough to cover current expenses.
What savings rate do I need to retire early?
At a 50% savings rate, you can retire in roughly 17 years. At 65%, about 10 years. At 75%, about 7 years. The relationship is logarithmic — your savings rate matters far more than your income or investment returns for determining time to financial independence.
How do I calculate my FIRE number?
Your FIRE number is your expected annual retirement spending multiplied by 25, assuming a 4% withdrawal rate. For example, if you plan to spend $50,000 per year in retirement, your FIRE number is $1,250,000. Adjusting to a 3.5% rate for early retirement raises it to approximately $1,430,000.
Plan your financial future
Pick your decision. Tap through a few screens. Get a confident answer in under 60 seconds.
Model My Decision