The Roth vs Traditional 401(k) Calculator Pack — Seven linked calculators, every formula checked by recalculation

Seven calculators for one choice: Roth or traditional 401(k). Start with sheet 1, which compares the two at the same take-home cost, then sheet 2 for the retirement tax rate at which they tie -- 21.54% on the worked example once the traditional tax saving is invested. Sheet 3 handles the employer match, which lands in the pre-tax side whichever you choose. Every tax rate is one you enter; nothing here computes brackets, files anything or tells you which to pick. 2026 limits are from the IRS and are inputs you can update. Every formula was recalculated and checked against an independent implementation before this shipped.

What is in it

7 calculators, one per sheet. Overwrite the blue cells with your own numbers and everything else follows — nothing is locked, there are no macros, and it opens in Excel, Numbers, LibreOffice and Google Sheets.

• Same paycheck cost — For the same take-home cost, which ends with more to spend?
• Break-even retirement rate — At what retirement tax rate do Roth and traditional tie?
• With an employer match — With a match, what does each choice leave you after tax?
• Investing the tax saving — If you invest what traditional saves you, who comes out ahead?
• Contribution to max out — How much per paycheck reaches this year's limit?
• Paycheck impact — How much smaller is each paycheck under Roth vs traditional?
• A split strategy — What does splitting between Roth and traditional do to the risk?

Every formula was checked

This pack contains 57 formulas. Before it was published, every one of them was recalculated by a spreadsheet engine and compared against an independent implementation of the same arithmetic written in Python. All 57 agreed to within a cent, and the workbook carries a Verification sheet saying so.

That is an unusual thing to be able to claim about a spreadsheet, and it is the main reason to buy this one rather than download a free template. A formula that looks right and is wrong is worse than no formula at all, because you will act on it.

What each calculator assumes

There is a sheet listing this, because a calculator that hides its assumptions is just a number generator:

• Same return in both accounts, contributions at the end of each year, the whole traditional balance taxed at the one retirement rate you enter. Both rates are yours; the pack computes no brackets.
• The second break-even assumes the tax saving is invested every year at the same return and its gains are taxed once, at the end, at the rate you enter. Yearly tax on dividends is ignored, which flatters the traditional side slightly.
• The match is modeled as pre-tax, per the IRS designated Roth account page. SECURE 2.0 lets a plan offer Roth treatment of employer contributions; if you elect that, the match is taxed now instead, which this sheet does not model. Vesting is ignored.
• The tax saving is invested every year at the same return. Gains are taxed once, at the end, at the rate you enter; yearly tax on dividends and the step-up or loss rules are ignored.
• Your plan may cap the percentage you can elect, may take deferrals from bonuses differently, and may stop at the limit or not -- check with your plan. Employer contributions do not count against this limit. The 50+ catch-up applies only if your plan allows it, and higher earners may be required to make catch-ups as Roth; check your plan.
• Social Security and Medicare are withheld on 401(k) deferrals either way, so they do not change the difference. Withholding tables only approximate your marginal rate; the true difference shows on your tax return.
• Equal paycheck cost across the choices. Each account earns the same return. The two test rates are yours; neither is a forecast.

What this is not

Not financial, tax or legal advice, and not a recommendation to buy, sell, borrow or sign anything. These are calculators: they show what a choice costs, not which choice is right for you. Where a published rate or threshold is used it is the one current when the pack was built — those change, the arithmetic does not.

Honest about the format

One .xlsx workbook, 7 calculator sheets plus Start Here, Assumptions and Verification. Not a PDF, not a physical product, not a Notion template. Available immediately after purchase; nothing ships.

Refunds

If this isn't what you expected, email me within 30 days and I'll refund you in full — no need to explain. Because it's an instant download I can't take the file back, so I'd rather you just had your money back.