Five Assumptions You Should Clarify Before Running Any FIRE Calculation
FIRE calculations can look precise, but without clear assumptions, the results can be misleading. Understanding assumptions is the foundation of sustainable planning.
Financial Independence (FIRE) GuideConcept to Planning
We organize core FIRE concepts, common myths, and estimation methods & assumptions to help you understand 'how much assets you need' with clear assumptions and steps.
Content is focused on education and knowledge sharing, with tools to help apply concepts to your personal situation.
FIRE Fundamentals
Understand the core concepts of Financial Independence (FIRE), common terminology, and basic principles. Clarify that early retirement isn't just about stopping work, but adding flexibility to life choices.
Estimation Models & Assumptions
Learn how key assumptions like withdrawal rates, investment returns, and inflation affect results, and understand why required asset sizes vary significantly under different conditions.
Long-term Planning
Move beyond single calculations to think about long-term planning. Understand how adjusting expenses, contributions, and goals at different life stages impacts your overall FIRE path.
What is FIRE? Why is everyone's number different?
FIRE (Financial Independence, Retire Early) is often translated as 'Financial Freedom, Early Retirement', but its focus is not just 'Retirement', but giving you more freedom in life choices: you can choose to work, or choose to pause; pursue a more meaningful career, or save time for family, health, and hobbies.
Most people use 'Withdrawal Rate' to estimate the assets needed for FIRE. A common practice is to calculate target assets based on annual expenses. For example, if you need $60k a year, assuming a conservative withdrawal strategy, you get a 'target asset range'. But what's often overlooked is that everyone's FIRE number depends on assumptions: will your expenses change with age? do you have a mortgage? market volatility, inflation, and additional income sources.
Therefore, 'FIRE Calculation' is not about getting a magic single number, but establishing a set of discussable and adjustable assumptions, and verifying them repeatedly under different scenarios: is the plan still valid if returns drop? if expenses rise? if you stop investing or change jobs? When you include these factors, FIRE turns from a slogan into an executable roadmap.
On this site, you will see articles ranging from FIRE basics, route comparisons (Lean/Barista/Fat FIRE), to common calculation errors and scenario simulations. You can also use our tools to apply the same methods to your own numbers, quickly viewing the differences in results under different assumptions.
Start Learning Here
FIRE Fundamentals
Understand withdrawal rates, the 25x rule, inflation, and return assumptions.
Choosing a Path
Differences between Lean / Barista / Coast / Fat FIRE and who they are for.
Calculation Methods
How to build a trackable planning model using expenses, contributions, and returns.
Common Myths
Why do many people calculate their FIRE number incorrectly?
Scenario Planning
Impact of stopping contributions, career changes, mortgages, and parenting on FIRE.
Tools & Templates
Quickly build comparable calculation versions with minimal data.
Learn & Grow
Latest from our blog
Insights, strategies, and tips for your FIRE journey.
How Does Pausing Investments for 3–5 Years Affect Your FIRE Timeline?
Most FIRE models assume continuous investing, but real life often includes pauses. This article explores how temporary investment breaks impact long-term FIRE plans.
Why the 4% Rule Doesn’t Work the Same for Everyone
The 4% rule is often treated as a universal FIRE formula, but in reality, it’s a historical reference—not a one-size-fits-all solution.
How We Approach FIRE Calculation
Our calculations and articles use adjustable assumptions to show result differences, such as investment returns, withdrawal strategies, and expense changes. Living conditions vary greatly, so we prioritize 'understanding models and limitations' over pursuing a single answer. You can use the content here as a starting point for building a planning framework, then adjust and verify based on your own situation.
Learn more: Methodology & AssumptionsSupplementary Tools (Reference)
If you wish to further verify differences in the above calculation assumptions under different scenarios, we have organized supplementary calculation tools for your reference after understanding the methodology.
FIRE Calculation Tools Guide (FirePath) →