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Retirement learning center · reviewed October 10, 2026

IRA pro-rata rule calculator

The central calculator estimates how documented after-tax basis is allocated in a supported annual IRA scenario. The explanation and inputs matter as much as the number.

2025 standard rules · 2026 form projections
  1. 1. Enter IRA details
  2. 2. Review tax exposure
  3. 3. Explore and export

Your IRA & conversion inputs

One IRA owner per calculation. All amounts are USD. Initial values are a sample; replace them with your records.

?Total net traditional IRA-to-Roth conversions in this calendar year; conversions have no annual contribution limit.
?Entire value of your own traditional and rollover IRAs, including basis. SEP/SIMPLE values go below.
?Reconcile prior Form 8606 line 14. Do not count the same contribution here and below.
?Regular IRA limit: $7,500 / $8,600 at age 50+; shared with regular Roth contributions and subject to taxable compensation.
?Traditional SEP IRA value; employer contributions are not regular nondeductible contributions.
?Traditional SIMPLE IRA value. Transactions within its first two years need review.
?Portion of current-year contributions made the following year. Excluded from this year's allocation basis on line 5.
Explore a different year-end balance
User-supplied assumption; state and local taxes excluded.
Step 2 · explainable allocation

Your conversion breakdown

2026 estimate using the 2025 Form 8606 structure. Final 2026 form instructions have not been verified.

Taxable conversion
$5,250.00
Tax-free conversion
$1,750.00
Remaining basis
$5,250.00
Estimated incremental federal tax
$1,260.00
Total relevant basis
$7,000.00
Year-end applicable IRA value
$21,000.00
Other taxable distributions
$0.00
Total distributions and conversions
$7,000.00

This is a planning estimate, not a complete tax return. Credits, deductions, capital gains stacking, NIIT, Medicare IRMAA, Social Security taxation, state/local taxes and early distribution penalties are excluded. Spouses calculate separately.

  • 2026 Form 8606 projection uses the finalized 2025 structure; final 2026 instructions were not verified.

Saving is optional. It stores financial values locally, unencrypted, and lets related tools reuse them. Reset clears your saved scenario.

Step 3 · explore your options

Compare conversion and reverse rollover strategies →Plan conversions over multiple years →Check your tax documents →
Preparation worksheet · 2026

Form 8606 line-by-line preview

Official 2025 form

Standard Part I/II allocation only. No IRS approval or filing submission is implied. No-distribution years skip allocation lines on the actual form; basis is retained. Reconcile with Forms 1099-R, 5498 and prior Forms 8606.

Supported Form 8606 calculations (provisional structure)
LineMeaning / calculationAmount
1Current-year nondeductible contributions$0.00
2Prior-year basis$7,000.00
3Combined basis$7,000.00
4Contributions made after December 31$0.00
5Basis available for allocation$7,000.00
6December 31 IRA values + outstanding rollovers$21,000.00
7Other eligible IRA distributions$0.00
8Net Roth conversions$7,000.00
9Allocation denominator (6 + 7 + 8)$28,000.00
10Nontaxable ratio (5 ÷ 9, capped at 1)0.250000000000000000
11Nontaxable conversion (8 × 10)$1,750.00
12Nontaxable other distributions (7 × 10)$0.00
13Total basis used (11 + 12)$1,750.00
14Remaining basis (3 − 13)$5,250.00
15aOther taxable distributions (7 − 12)$0.00
15bQualified disaster amount (unsupported)$0.00
15cOther taxable distributions, standard case$0.00
16Conversions$7,000.00
17Nontaxable conversions$1,750.00
18Taxable conversion (16 − 17)$5,250.00

IRS Form 8606 instructions · Calculation assumptions · Supported and review-only scenarios

A simple teaching example

With $7,000 of available basis, a $7,000 conversion and $21,000 remaining IRA value, the simplified pool is $28,000. One quarter of the conversion is tax free: $1,750. The other $5,250 is taxable. This example assumes no other distributions, late contributions or adjustments.

Use the detailed inputs when needed

The advanced workspace distinguishes contribution timing and other annual transactions. Review warnings before exporting, and use a professional for unsupported exceptions.

Sources and next steps

Reviewed October 10, 2026. This independent educational website is not affiliated with the IRS. Special transactions need professional review.

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