Gather every IRA, not every retirement account
Add traditional, SEP and SIMPLE IRA balances. A 401(k), 403(b), governmental 457 plan and Roth IRA are not part of this IRA denominator.
Backdoor Roth IRA planning
How much of your Roth conversion may be taxable?
Model the IRA pro-rata rule using the same building blocks as Form 8606, then check whether a direct Roth contribution or a workplace-plan “mega backdoor” may fit instead.
IRA pro-rata estimator
Enter your conversion-year totals
Use the totals for all of your traditional, SEP and SIMPLE IRAs—not only the account being converted.
Usually last year’s Form 8606, line 14.
Do not include a contribution made in 2027 for 2026 here.
Combined year-end value of traditional, SEP and SIMPLE IRAs.
Exclude the Roth conversion itself.
%
Optional combined rate for a rough tax-cost estimate.
Direct Roth check
Do you need the backdoor at all?
Direct Roth IRA eligibility depends on filing status and modified adjusted gross income (MAGI). This quick screen shows the 2026 phase-out band; it does not calculate the reduced contribution inside the band.
Your screen
Above the direct-contribution range
At this MAGI, a direct Roth IRA contribution is unavailable under the 2026 limit. A backdoor strategy may be worth discussing if the other rules fit.
- Single / head of household$153,000–$168,000 phase-out
- Married filing jointly$242,000–$252,000 phase-out
- Married filing separately, lived together$0–$10,000 phase-out
Workplace plan calculator
Estimate mega backdoor Roth room
A mega backdoor strategy is separate from the IRA backdoor. It depends on a 401(k) or similar plan accepting after-tax employee contributions and allowing an in-plan Roth rollover or a suitable distribution.
Exclude catch-up contributions.
Include after-tax amounts already contributed and forfeitures allocated.
Potential additional after-tax room
$38,500
That is the remaining space below the lower of 100% of compensation or the $72,000 annual-additions cap. Your plan can impose a lower limit.
2026 annual-additions ceiling used$72,000
Contributions already counted$33,500
Regular elective-deferral limit$24,500
Age-based catch-up contributions are outside the $72,000 annual-additions limit. Plan terms, testing and payroll cutoffs can reduce what is actually available.
Planning library
Go deeper before you move money
Each guide has a focused URL and links back to the calculators.
GUIDE 01
The pro-rata rule
See why every traditional, SEP and SIMPLE IRA enters the calculation.
GUIDE 02Planning sequence
A careful order of operations, records and year-end checks.
GUIDE 03Backdoor vs. mega backdoor
Compare the account paths, limits and plan requirements.
GUIDE 04Common questions
Conversions, old IRAs, workplace plans and carried basis.
Guide 1
The pro-rata rule, without the fog
Find your after-tax basis
Your basis is the nondeductible money already taxed. Prior-year basis generally carries from Form 8606, and a current nondeductible contribution adds to it.
Use the December 31 value
The year-end balance matters even if the conversion happened months earlier. A pre-tax IRA still open on December 31 can make part of the conversion taxable.
Allocate the same percentage
The basis ratio applies across distributions and conversions. Form 8606 computes the nontaxable amount and carries unused basis into a later year.
Guide 2
A practical planning sequence
This is a conversation map, not personalized tax advice. Account mechanics and timing vary by custodian and employer plan.
Check direct Roth eligibility first
If your MAGI is below the applicable 2026 phase-out, a direct Roth contribution may be simpler. Inside the phase-out, the permitted direct amount is reduced.
Inventory pre-tax IRA money
Record all traditional, SEP and SIMPLE IRA balances and any existing nondeductible basis. An old rollover IRA is easy to overlook.
Ask whether a workplace plan accepts roll-ins
The IRS says a workplace plan may accept an IRA rollover if its plan language allows it. Moving eligible pre-tax IRA money into a plan can change the year-end IRA denominator, but confirm eligibility and investment/fee tradeoffs first.
Document the contribution and conversion
Nondeductible traditional IRA contributions are reported on Form 8606. Keep the contribution confirmation, conversion confirmation, year-end statements and tax forms together.
Recheck December 31
Confirm the year-end value across every traditional, SEP and SIMPLE IRA. This is the number that can surprise an otherwise careful conversion.
Guide 3
Backdoor Roth vs. mega backdoor Roth
The similar names hide two different account paths.
Backdoor Roth IRA
- Uses a traditional IRA contribution followed by a Roth IRA conversion.
- 2026 IRA contribution limit: $7,500, or $8,600 at age 50+; taxable compensation can be a lower cap.
- The pro-rata calculation aggregates traditional, SEP and SIMPLE IRAs.
- Generally reported with Form 8606 when nondeductible basis or a conversion is involved.
Mega backdoor Roth
- Uses after-tax employee contributions inside an eligible workplace plan.
- 2026 annual additions are limited to the lower of 100% of compensation or $72,000, excluding catch-up contributions.
- Requires plan support for after-tax contributions and a Roth conversion or rollover path.
- Employer contributions and regular elective deferrals consume the same annual-additions space.
Guide 4
Frequently asked questions
Does the income limit block a Roth conversion?
The 2026 income phase-outs shown above apply to direct Roth IRA contributions. The tax result of a conversion depends on basis, IRA values, distributions and other facts; this calculator focuses on the pro-rata allocation.
Why does a SEP or SIMPLE IRA change my result?
Form 8606 combines traditional, SEP and SIMPLE IRAs when determining the nontaxable share. The name or custodian of the account does not isolate its dollars from that calculation.
Does a 401(k) count in the IRA pro-rata denominator?
No. The IRA calculation uses traditional, SEP and SIMPLE IRAs. A workplace plan can still matter strategically if it accepts eligible pre-tax IRA roll-ins, and a separate annual-additions limit governs mega backdoor room.
Why can my conversion be taxable even after a nondeductible contribution?
A nondeductible contribution creates basis; it does not label specific IRA dollars as after-tax. If the denominator also includes pre-tax IRA money, the conversion contains a proportional taxable share.
What happens to basis not used this year?
Unused nondeductible basis generally carries forward on Form 8606. Keep your filed forms: losing the basis record can make future reporting difficult.
Primary references
Built from IRS guidance
Limits are for tax year 2026. The calculator is a planning aid, not a substitute for Form 8606 instructions or professional advice.
- IRS: 2026 401(k), IRA and Roth income-limit changes
- IRS: IRA contribution limits
- IRS Publication 590-A: IRA contributions and nondeductible contributions
- IRS Publication 590-B: IRA distributions and Roth conversions
- IRS: 401(k) and profit-sharing contribution limits
- IRS: rollovers of after-tax workplace-plan contributions
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