Here's another one that gives a small advantage to Roth:
https://www.americanfunds.com/individual/planning/tools/traditional-vs-roth-401k-403b-analyzer.htm
Here's one that gives a small advantage to traditional:
https://www.dinkytown.net/java/Compare401k2.html
I think it's fair to say that the consensus of these calculators is that there negligible difference even when going from 33% -> 20%.
That second one is the
closest to realistic.You still have to plug in the applicable marginal rate for pre-retirement (the rate you're avoiding on those dollars right now) and then plug in an expected average rate for retirement, but it (unlike the others) has some rational values at an initial glance. And it does favor traditional, which is entirely expected given basic mathematical realities.
Basically, it should hold that if you're avoiding 28% marginal rates now and invest the savings, you would have to pay 28% average in the future in order for the Roth to be on equal ground. Any average tax rate less than that is a feather in the traditional 401K's cap.
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Edit: Here is the result of the second calculator that
aimed for equality, for explanation:
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Edit 2: I'll redact part of the above, including all of edit 1. I noticed a variable I did not account for which impacts the result. It still favors traditional (with a sensible future tax rate), but not by as much as previously forecast. Flip the current contribution type over to Roth and it will be evident. It's probably due to the combination of income taxes due on the current excess if switching to traditional, and then the capital gains rate on earnings in side investments. These are reasonable adjustments.
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Edit 3: After further analysis, and in the interest of kind of me eating a little crow, I think that the "dinkytown" calculator is fairly spot on, and if I played with some of the other calculators (forget that one that has wrong calculations in it), perhaps I could get them in the right ballpark, as well. Here is the calculation that aims for the break-even point, given some income assumptions:
This goes with an income level that could put all of the 401K into the 28% marginal rate [update: in reality, income level doesn't even matter in this exercise, put it at 0 for all its worth]. It holds the current tax to be avoided at 28% (the marginal rate), and the retirement rate at the break-even average rate (the tipping point between favoring one side or the other). I had forgotten this, but I had arrived at similar numbers in the past when performing my own calculations, and this brought that back to memory. Not explicitly shown here, but the things I mentioned in edit 2 can reasonably be assumed to be included in here, and the takeaway is that based on maxing out a 401K traditionally, you would funnel the tax savings into a taxable investment account, you would pay roughly 20% capital gains on proceeds there, you would progress through the marginal rates on the income from the 401K, and you would need to stay at or below ~23% taxes on average in order to come out ahead of just paying the 28% up front and going with the Roth. (Not shown: how state and local income taxes factor in and move the numbers.) It's an interesting exercise, I'll give you that.
So uh, look at your own effective tax rates. Make your call. I've looked at mine, and it's actually in the teens, and not even close to 20. I'm comfortable with my pre-tax choice, but then, I itemize a lot. Your mileage may vary.