FIRE Calculator
What you will learn
Separate spending assumptions and portfolio assumptions in a financial-independence estimate.
Try it on the maintained tool page
Open FIRE Calculator (opens in a new tab)
Record the spending and return assumptions in the estimate. Change one assumption and describe what the result cannot guarantee.
Keep this course tab open. Return here to answer the questions and continue to the next lesson.
Check your understanding
Answer each question, then open the explanation.
1. Does an assumed rate establish the return an investment will earn?
Show answer and why
Answer: No. It defines a model input.
Why: A correct calculation can still use assumptions that future markets do not deliver.
2. Why change one input at a time?
Show answer and why
Answer: To identify which assumption caused a difference in the result.
Why: Changing several inputs together makes that cause harder to isolate.
3. What should accompany a projected outcome?
Show answer and why
Answer: Its assumptions, time period and important omissions.
Why: Costs, uncertainty and excluded circumstances can change how useful the estimate is.
Key takeaways
- A projected return follows the assumed rate; it is not a guaranteed outcome.
- Change one input at a time to identify its effect.
- Record the time period, assumptions and costs or risks the model omits.
This course activity is for financial education. Check original sources and the tool’s stated assumptions before interpreting an output.
AI responses are for educational purposes. Always verify with official course materials.
This lesson teaches a concept. It is general education, not advice about your money. Before you act on anything you learn here, speak to someone licensed.
Sources and reference material
Primary sources and original reference material for the concepts discussed on this page.
- Investor.gov: Compound interest calculator and assumptions
- Investor.gov: Asset allocation, diversification and rebalancing
- IRS: Retirement plan definitions
References added 14 October 2026.
AI responses are for educational purposes. Always verify with official course materials.
This lesson teaches a concept. It is general education, not advice about your money. Before you act on anything you learn here, speak to someone licensed.
This lesson teaches a concept. It is general education, not advice about your money. Before you act on anything you learn here, speak to someone licensed.
