Backdoor Roth IRA Guide & Pro-Rata Calculator 2026-2030

Last verified: October 29, 2026

Non-Deductible Contribution

Contribute to a traditional IRA (no income limit on contributing; income limits apply only to the deduction, IRC 219(g)). Report it as nondeductible on Form 8606, Part I, which establishes basis.

Convert to Roth

Convert the traditional IRA to a Roth IRA and report it on Form 8606, Part II. Conversions have no income limit (IRC 408A(c)(3), (c)(5)(B)) and cannot be recharacterized (IRC 408A(d)(6)(B)(iii)).

Pro-Rata Calculation

If you hold other pre-tax traditional, SEP or SIMPLE IRA money at year-end, the pro-rata rule taxes part of the conversion. All IRAs are one contract. IRC 408(d)(2).

Pro-Rata Rule Calculator • IRC 408(d)(2)

The pro-rata rule aggregates ALL traditional, SEP and SIMPLE IRAs. You cannot convert only the after-tax dollars. Each conversion is a proportional mix of pre-tax and after-tax money, measured with year-end balances (IRC 408(d)(2)). 401(k) balances do not count.

Tax Year

2026 is IRS-published (Notice 2025-67); 2027-2030 are projected.

Filing Status

Age 50 or Older by Year-End

Adds the IRC 219(b)(5)(B) catch-up.

Assumed Annual Inflation (%) - projections

Used only for 2027-2030.

Modified AGI for Roth Purposes ($, optional)

Shows your direct Roth contribution limit. IRC 408A(c)(3).

Nondeductible Contribution for the Year ($) - Form 8606 Line 1

Prior-Year Basis ($) - Line 2

Line 14 of your last Form 8606.

Of Line 1, Made Jan. 1 to Apr. 15 of Next Year ($) - Line 4

Excluded from this year's ratio.

Value of All Traditional, SEP and SIMPLE IRAs at Dec. 31 After the Conversion ($) - Line 6

Include outstanding rollovers. The critical number; 0 gives a clean backdoor.

Other Traditional IRA Distributions in the Year ($) - Line 7

Not conversions, rollovers or QCDs.

Amount Converted ($) - Line 8

Blank assumes the contribution is converted.

Marginal Federal Rate on the Taxable Part

Flat-rate estimate; use the Roth Conversion Tax Impact Calculator for bracket math.

Enter your information above.

Mega Backdoor Roth & Additional Strategies

Your Elective Deferrals ($)

Blank uses the IRC 402(g) limit for the year.

Employer Contributions ($)

Match and profit sharing count toward 415(c).

Compensation ($, optional)

415(c)(1)(B): 100% of compensation.

Eliminating the Pro-Rata Problem

If pre-tax IRA balances create pro-rata exposure, consider rolling them into your current employer 401(k) if the plan accepts rollover contributions. This removes them from line 6 of Form 8606 so the conversion is mostly or entirely tax-free. Complete the rollover before December 31 of the conversion year, because line 6 is measured at year-end (IRC 408(d)(2)(C)).

Assumptions & sources

Projected figures are estimates. Where a tax year shows the "Projected - estimate, not IRS-published" badge, inflation-indexed amounts are projected from the latest IRS-published figures using the inflation rate you select and the rounding rule stated in the statute. They are not IRS-published and will differ from the final revenue procedure. Educational estimate only; verify against current primary authority before relying on any figure.

IRC 408A(c)(3), (c)(5), (d)(3), (d)(6)(B)(iii); IRC 408(d)(2); IRC 219(b)(5), (g); IRC 402(g); IRC 414(v)(3)(A); IRC 415(c), (d); IRC 4973(a); IRC 6693(b); Form 8606 (2025) lines 1-18; Notice 2025-67 (2026 limits); Notice 2014-54; IRS Pub. 590-A (2025).

Educational estimate only; not tax advice. See the full disclaimer.

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