After-Tax 401(k) Rollover Calculator

One account with two tax buckets

Enter the pre-tax balance and employee after-tax contribution basis of one non-designated-Roth employer-plan account. Earnings on after-tax contributions go in the pre-tax field, not the basis field. Then enter the eligible distribution amount. This calculator allocates that payment; it does not approve a distribution under your plan’s terms.

Partial payments contain both buckets

For an account with $80,000 pre-tax and $20,000 basis, a $50,000 partial distribution contains $40,000 pre-tax and $10,000 basis. Asking for $20,000 does not withdraw just the $20,000 basis: that payment contains $16,000 pre-tax and $4,000 basis. The remaining money stays in the account proportionally.

Separate destinations, coordinated instructions

The displayed route sends the entire pre-tax portion to a Traditional IRA or another eligible pre-tax destination, and the basis portion to a Roth IRA. Confirm that both receiving accounts accept the transfers, and coordinate simultaneous direct-rollover instructions with the administrator. Sending pre-tax money to Roth is a different taxable-conversion choice, not the tax-free split shown here.

$100,000 account: 80% pre-tax / 20% basis	Traditional destination	Roth basis destination
$20,000 payment	$16,000	$4,000
$50,000 payment	$40,000	$10,000
$100,000 payment	$80,000	$20,000

What this allocation cannot decide

There is no age or in-service distribution eligibility test here. The calculator does not use the year-end IRA balance rule for Form 8606, does not calculate a backdoor Roth IRA, and does not handle a designated Roth 401(k) account. It assumes a complete eligible distribution amount is rolled directly to the two destinations shown, with no cash retained.

Confirm that after-tax means basis, not designated Roth

An after-tax employee contribution to a non-Roth employer-plan account is different from a contribution to a designated Roth 401(k). In this allocation model, after-tax basis is the part of the supported non-Roth account that has already been taxed, while the remaining modeled amount is pre-tax. Earnings on an after-tax contribution are not automatically after-tax basis. Start from the administrator’s allocation record rather than guessing that every dollar labeled “after-tax” on an investment screen includes tax-free earnings.

Enter the balance and basis for the account the plan treats as relevant to this distribution. A record showing several separately accounted sources is not permission to combine or separate them however produces the largest Roth amount. The administrator determines the distributable sources and their accounting. This calculator applies a supplied ratio; it cannot certify the account’s basis history or replace a missing plan record.

A partial distribution keeps the supplied ratio

For the example account of $100,000 with $20,000 of basis, the after-tax share is 20%. A $50,000 distribution therefore contains $10,000 of modeled basis and $40,000 of pre-tax money. Moving only $20,000 does not make that entire payment basis: under the same ratio it contains $4,000 of basis and $16,000 of pre-tax money. The examples expose the allocation so a smaller payment is not confused with choosing only one tax component.

The result shows destinations for a supported split direct rollover, with the modeled pre-tax part directed to a traditional destination and basis directed to a Roth destination. It does not instruct the plan to send either payment. If the administrator quotes different components, reconcile the supplied source account and basis rather than changing a destination field to force a desired number. Total destinations should equal the modeled distribution; nothing in this model is retained as spendable cash.

Distribution permission comes before allocation

A ratio that adds up correctly does not mean you can take an in-service distribution or complete a conversion today. Distribution eligibility, a plan’s acceptance of instructions, the receiving account’s acceptance and any timing requirements are outside the calculation. A plan document can restrict a transaction even when the tax rules describe how an eligible transaction is allocated. Confirm these issues with the distributing and receiving institutions before using the output to plan transfers.

This is not the IRA year-end balance calculation associated with Form 8606. A “backdoor Roth” task involving traditional, SEP or SIMPLE IRA balances has a different record and formula. It is also not a designated Roth distribution tool. Keeping those questions separate avoids treating a useful basis-allocation result as proof that a broader Roth conversion strategy is tax-free. The calculator does not estimate your tax bracket, state tax or a complete conversion bill.

Keep a record of both destination payments

For an actual permitted transaction, retain the plan’s gross distribution, pre-tax amount and basis, and the amounts each receiving institution accepted. Check that those records describe the same transaction and account sources as your input example. Tax reporting may not use the same display wording as a calculator card. If the two records do not agree, ask the institutions to explain the discrepancy before assuming the output is authoritative.

For planning, vary the distribution amount while keeping the account ratio fixed and compare the two destinations. The exercise makes the allocation visible without changing the assumed source record. It does not forecast growth after rollover or recommend which investments to buy. A calculation error report should contain the fictional balance, basis, proposed distribution and expected arithmetic, not an identifying retirement statement.

Explanation maintained by the site operator. Methodology and limitations · Report a calculation issue.

Official sources

Rules checked October 5, 2026. Publication 590-A and Publication 560 use 2025 mechanics; indexed 2026 limits use Notice 2025-67.

Frequently Asked Questions

Can I withdraw only basis and leave pre-tax money?

Not under the proportional partial-distribution rule modeled here. The payment includes both account buckets.

Are earnings on after-tax contributions also basis?

No. Include those earnings in the pre-tax balance.

Is this the IRA Form 8606 calculation?

No. It models one non-designated-Roth employer-plan account, not aggregated IRA balances.

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