If you doubled federal individual income taxes for everyone in the US, you could pay each adult US citizen around $750/mo in UBI with that increase.

If you doubled ALL federal income taxes in the US, you could pay each adult US citizen ~$1500/mo in UBI.

And of course, the higher you set UBI, the less point there is to work like a chump and pay 2x current tax rates so other people don’t have to, so fewer people would work (which is one of the promises of promoters of UBI), meaning taxes would have more than double to make the payments.

The math is daunting because the number of people is so high.