Week 25 Day 7: Your Retirement Number: How Much Is Enough?

If you can withdraw 4% per year without running out of money, then you need 25 times your annual expenses (because 100% / 4% = 25x). This is the simplest and most powerful equation in personal finance. Annual expenses of $40,000: need $1,000,000. Annual expenses of $60,000: need $1,500,000. Annual expenses of $100,000: need $2,500,000.

Refinements to your retirement number: (1) Subtract guaranteed income. If Social Security provides $30,000/year and your expenses are $60,000, you need to cover $30,000 from your portfolio. $30,000 x 25 = $750,000. Much more achievable than $1,500,000. (2) Plan for healthcare. Fidelity estimates $315,000 for a 65-year-old couple's healthcare costs in retirement. Factor this into expenses. (3) Account for taxes. If your withdrawals are from a 401(k) (taxed as income), you need to withdraw more to net the same spending money. A $60,000 need may require $70,000-75,000 in gross withdrawals. (4) Build an inflation margin. If you think you need $50,000/year today, plan for $60,000 to account for future inflation. (5) Consider your timeline. The 25x rule assumes 30 years. If you retire at 40 (50-year horizon), use 30x or 33x instead. If you retire at 65 with a pension covering half your expenses, 20x of the uncovered portion is sufficient. Example: Annual expenses: $70,000. Social Security: $35,000. Gap: $35,000. Required portfolio: $35,000 x 25 = $875,000. Add $100,000 for healthcare cushion: $975,000. Round up for safety: target $1,000,000.

The '25x rule' (the inverse of the 4% withdrawal rate) is a useful heuristic but oversimplifies the retirement adequacy calculation. A comprehensive analysis requires modeling: (1) stochastic investment returns (Monte Carlo simulation with 10,000+ scenarios), (2) inflation-adjusted spending needs (potentially declining in real terms as retirees age -- the 'retirement spending smile' documented by Blanchett, 2014), (3) longevity risk (modeling mortality probabilities, not just a fixed 30-year horizon), (4) healthcare costs (which grow at approximately CPI+2%, faster than general inflation), (5) tax optimization (Roth conversions, capital gains harvesting, Social Security taxation management), and (6) behavioral guardrails (willingness and ability to reduce spending in down markets). Finke, Pfau, and Blanchett (2013) showed that the safe withdrawal rate is a function of beginning-of-retirement asset allocation, real bond yields, and equity valuations. At current valuations (CAPE 35+) and bond yields (4.5%), their model suggests a 30-year safe withdrawal rate of approximately 3.5-4.0%. For a more personalized calculation, the open-source cFIREsim and FIRECalc tools run historical simulations with user-specified inputs. Commercial tools like Boldin (formerly NewRetirement, $120/year) incorporate Social Security optimization, tax planning, Roth conversions, and healthcare modeling. The 25x rule gets you in the right ballpark; these tools refine the estimate.