[floundy]

No. Pro rata is Latin for “in proportion.” It’s one dollar for one dollar. If you add $7k to your tIRA to do the backdoor Roth, you also must convert $7k of existing funds which becomes taxable income. So you pay your marginal tax rate, on half the amount.

IMO not that big of a deal to contribute $7k, convert $7k, and pay $2-3k in taxes to get $14k in the Roth space that will grow tax free forever. Most people are too pre-tax heavy in their retirement strategies anyway.

[aobdev]

I'm not familiar with the strategy you're describing, but this is not how it works for the majority of backdoor Roth contributors.

If you have $100k pre-tax in a trad IRA, contribute 7k after tax for the purpose of rolling into a Roth, then you will owe income tax on the proportion of 100/107*7k, or $6,542.

You're still limited to 7k annual (for 2025) so the 14k you describe must be something else.