Coast FIRE Part-Time Calculator

Coast FIRE is the point where your existing investments are large enough to grow to your full retirement portfolio target by your target retirement age with zero additional contributions. The formula is: Coast FIRE Number = Target Retirement Portfolio / (1 + real annual return)^years to retirement. For example, if you need $1.5 million at age 60, you are currently 35, and you assume a 5% real return, your Coast FIRE number is $1,500,000 / (1.05)^25 = approximately $443,000. Once your portfolio reaches $443,000, compound growth alone will carry it to $1.5 million by age 60 without any further contributions. You only need to earn enough to cover current living expenses, which opens the door to part-time, freelance, or lower-stress work.

The calculator determines the minimum gross income needed to cover your annual living expenses after taxes, without touching your investment portfolio. This is the income floor you must earn from part-time or freelance work to sustain the coast phase. If your annual expenses are $40,000 and your effective tax rate is 20%, you need approximately $50,000 in gross part-time income. The calculator also factors in health insurance costs, which are often the largest single expense for Americans leaving full-time employment: COBRA averages $500-$700/month for individuals, while ACA marketplace plans with subsidies based on your reduced coast-phase income may cost significantly less.

The primary risk is sequence of returns during the coast phase. A major market downturn early in the coast period (before your portfolio has compounded significantly) can delay your projected retirement by 3-7 years. Building a buffer of 10-20% above your calculated coast number provides meaningful protection. A second risk is inflation exceeding your assumption: if real returns are 3% instead of 5%, the compounding shortfall is substantial over 20-25 years. Third, lifestyle inflation during the coast phase can increase your retirement spending target, moving the goalposts. Mitigation strategies include maintaining the ability to increase part-time hours temporarily, keeping expenses below the projected level, and having a contingency plan to make small additional contributions if the portfolio falls below its projected growth trajectory.

Coast FIRE means your portfolio fully covers future retirement through compound growth, and you only earn income to cover current expenses without touching the portfolio. Barista FIRE means your portfolio covers part of current expenses through withdrawals, and you work part-time to cover the rest plus potentially gain employer health benefits. Lean FIRE means you have already reached full financial independence but at a minimal spending level ($25,000-$40,000/year) with no earned income. Coast FIRE is appropriate when your portfolio has crossed the coast threshold but you have not yet reached full FIRE. Barista FIRE is appropriate when your portfolio has not reached the coast threshold but you want to reduce work intensity by supplementing portfolio withdrawals with part-time income.

Conservative coast projections use 4-5% real (inflation-adjusted) returns for diversified equity portfolios, which corresponds to approximately 7-8% nominal returns minus 3% inflation. The historical US stock market has returned approximately 7% real over the long term, but future returns may be lower due to elevated valuations and demographic trends. Using 5% real is a common moderate assumption. For a more conservative projection, use 4% real. The difference between 4% and 6% real return assumptions can change your coast number by 30-50% for time horizons of 20+ years, so this assumption is one of the most impactful inputs in the calculator.

Common coast-phase income sources include freelance consulting leveraging your full-time career skills at premium hourly rates ($50-$200/hour depending on expertise), part-time employment in a lower-stress role or industry (retail, education, nonprofit), teaching or tutoring (adjunct faculty, online courses, coding bootcamp instruction), seasonal or project-based work, creative pursuits with income potential (writing, photography, content creation), and rental income from property. The ideal coast-phase work provides enough income to cover expenses, offers health insurance or makes marketplace insurance affordable through lower reported income, and aligns with how you want to spend your time.

The coast age depends on how early you started saving, your savings rate, and your target retirement portfolio. Someone who saved aggressively (40-50% savings rate) starting at age 22 could reach their coast number by age 30-35. Someone who started saving 15-20% at age 30 might reach their coast number by age 40-45. The mathematical relationship means that earlier savers benefit enormously because their money has more time to compound. A dollar invested at age 25 has approximately 5.4 times the value at age 60 (at 5% real return) compared to a dollar invested at age 40. The calculator shows your specific coast age based on your inputs.

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No. This tool provides planning estimates based on compound growth models and historical return data. Coast FIRE decisions involve complex personal, tax, insurance, and career factors that require professional guidance for implementation. The projections assume constant real returns, which differs from actual market behavior where returns vary significantly year to year.