Mega Backdoor Roth Calculator
After contributing the $24,500 pre-tax/Roth elective deferral, you can contribute after-tax dollars up to the $72,000 total limit — then convert to Roth. Calculate your mega backdoor space.
Your 401(k) Contributions (2026)
Total Contribution Limit
$72,000Max After-Tax Space
$37,500After-Tax Remaining
$17,500Conversion Analysis
Tax on Gains
$480
Gains on after-tax before conversion are ordinary income
Net Roth Conversion
$21,520
After-tax basis + gains − tax
In-plan Roth rollover: 5-year clock starts on conversion date. Each conversion has its own 5-year clock.