Roth Conversion Calculator

How it works

A Roth conversion moves money from a traditional IRA to a Roth IRA. The amount converted is added to your taxable income for the year, so it is taxed at your ordinary rates on top of your other income. The table shows how much of the conversion lands in each federal bracket.

If you convert, the Roth grows and is withdrawn tax free (once qualified). If you don't, the traditional IRA grows by the same return but every dollar withdrawn is taxed at your retirement rate.

Paying the tax with money outside the IRA keeps the whole amount growing in the Roth. The fair comparison then credits the no-conversion side with that outside cash, invested in a taxable account. Paying the tax out of the conversion puts less into the Roth.

The break-even retirement tax rate is the rate at which converting and not converting come out the same. Expect a higher rate than that in retirement and converting wins; expect lower and it loses.

Formula

tax now  = tax(other income + amount) − tax(other income)    (or amount × flat rate)
G        = (1 + r)^n
tax from the conversion:  convert = (amount − tax) × G;  keep = amount × G × (1 − t_retire)
tax from outside cash:    convert = amount × G;  keep = amount × G × (1 − t_retire) + side
side     = tax × G − t_gains × (tax × G − tax)
break-even t_retire = tax ÷ amount  (from conversion);  side ÷ (amount × G)  (outside)

Example

A single filer with $60,000 of taxable income in 2026 converts $30,000. All of it falls in the 22% bracket ($50,400–$105,700), so the conversion adds $6,600 of federal tax: 22% of the amount.

Paying the $6,600 from savings and leaving the Roth to grow at 6% for 20 years gives $96,214.06, tax free. Not converting leaves $96,214.06 in the traditional IRA, worth $75,046.97 after a 22% retirement tax, plus the $6,600 kept in a taxable account, which grows to $21,167.09 and nets $18,982.03 after 15% tax on its $14,567.09 gain. Not converting totals $94,029.00, so converting comes out $2,185.06 ahead, and the break-even retirement rate is 19.73%.

Assumptions and limitations

• Federal income tax only, from the brackets for the tax year you choose (Rev. Proc. 2025-32 for 2026, Rev. Proc. 2024-40 for 2025). State tax, and any effect of the extra income on credits, deductions that phase out, Social Security taxation, Medicare premiums (IRMAA) or the net investment income tax, are not included. Use the flat-rate option to apply a combined rate.
• If you have made nondeductible (after-tax) contributions to any traditional IRA, the pro-rata rule on Form 8606 makes part of the conversion tax free. This calculator assumes the whole amount is taxable.
• If you are under 59½ and pay the tax out of the conversion, the amount withheld is a distribution that may also owe the 10% additional tax; this is not added here.
• The return and retirement tax rate are assumptions you enter. The traditional IRA is assumed to be withdrawn in full at the end of the period at that single rate; required minimum distributions are not modelled.
• The outside cash is assumed to be invested at the same return, with its gain taxed once at the rate you enter.
• Earnings are tax free only in a qualified distribution: at least five years after your first Roth IRA contribution and after age 59½ (or disability or death). Separately, each conversion starts its own five-year period; withdrawing converted amounts within it before 59½ may owe the 10% additional tax (Publication 590-B). Neither is modelled.
• Taxable income without the conversion cannot go below $0, so deductions you have not used up (for example, a standard deduction larger than your other income) are not credited against the conversion. If yours would shelter part of it, enter a lower conversion amount or use the flat-rate option.
• This is an estimate for planning. It is informational and educational and is not financial, tax or legal advice.

Frequently asked questions