Two numbers matter. Your FIRE target is annual spend divided by safe withdrawal rate. Your FIRE date is when your portfolio compounds to that target.
FIRE age 48
A decade-plus. Real return assumptions matter more at this horizon. Sensitivity-check at 3.5% SWR if you'd retire before pension age, and run the math against a flatter return.
Real return is after-inflation. The 4% safe withdrawal rate is the Trinity-Study default for 30-year horizons. For 40+ year early-retirement horizons, many planners now recommend 3.5%. Liquid vs locked split assumes a 60 / 40 contribution allocation across the two buckets for simplicity.
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For 30-year retirements: yes, with caveats. For early retirees with 40-50 year horizons, many planners now recommend 3.25-3.5% as the default. The original Trinity Study didn't model multi-decade retirements through expected lower future returns. Use 4% as the headline number but stress-test at 3.5% if you'd retire before 50.
Return after inflation. Using real returns means everything in the calculator is today's value. No need to mentally inflate the FIRE target, it's what it buys you today, not nominal currency 30 years from now.
No. Your home is wealth but you can't draw 4% of it for groceries without selling or refinancing. Include in net worth, exclude from FIRE math. If you plan to downsize at retirement, model the freed equity as a one-off contribution to the portfolio in that year.