Mega Backdoor Roth IRA Calculator

Mega backdoor Roth explained: How it works: contribute after-tax dollars to 401(k) above the $23,000 pre-tax limit (2026); total 401(k) limit: $69,000 (employee + employer contributions + after-tax); after-tax room: $69,000 - $23,000 pre-tax - employer match = leftover for after-tax; immediately convert after-tax to Roth (in-plan Roth rollover or roll to Roth IRA); gain is tax-free thereafter; Example: $23,000 pre-tax + $10,000 employer match + $36,000 after-tax = $69,000; convert $36,000 to Roth; $36,000 grows tax-free forever; Availability: requires 401(k) plan that allows after-tax contributions; after-tax in-service withdrawals (for rollover out); large employers (Google, Amazon, Microsoft) typically allow this; self-employed: solo 401(k) — maximum flexibility, easiest mega backdoor Roth; Backdoor Roth IRA (traditional): $7,000/year limit; contribute non-deductible IRA → immediately convert to Roth; total: $36,000 + $7,000 = $43,000/year additional tax-free investing.

Mega backdoor Roth 30-year savings: Assumptions: $36,000/year after-tax → Roth, 8% annual return; Roth account after 30 years: $36,000 x 30 years compounding = $4.1M; All $4.1M is tax-free; Taxable account equivalent: $36,000/year, 8% gross, 23.8% capital gains tax (long-term); After-tax return: approximately 6.5%; 30-year value: $3.0M; Tax drag: $1.1M less (27% less wealth); Over 40 years (age 25-65): Roth: $10.2M tax-free; Taxable: $7.3M; Tax savings: $2.9M; Key benefits: no required minimum distributions from Roth; heirs inherit tax-free (10-year withdrawal rule for inherited Roth); state tax-free in most states; Asset location strategy: put highest-returning assets in Roth (growth stocks, VC/PE exposure) for maximum tax-free compounding; IRS risk: Congress has repeatedly threatened to limit backdoor Roth — use it while available.

Family offices (single or multi) make sense at $50M+ in investable assets. Below that, private banking (JP Morgan Private Bank, Goldman Sachs PWM, UBS) offers similar services with lower minimums ($5-25M). Family offices provide consolidated reporting, direct deal access, and custom investment mandates unavailable at private banks. Multi-family offices (Bessemer Trust, Glenmede) offer a middle ground at $10M+ with family-office-level service at lower cost.

Most wealth advisors recommend 3-5% of liquid net worth in cash/cash equivalents for UHNW individuals — enough to cover 12-24 months of lifestyle expenses plus opportunistic investments. Excess cash above this benchmark costs 5-8% annually in opportunity cost vs. diversified portfolios. Treasury bills, money market funds, and short-duration bonds provide liquidity with yield while maintaining capital preservation objectives.