There's also the cost of working (commuting, clothes, etc). You could try to come up with an exact number like 43.5%, but a rough estimate is to just double the cost of something to get how much you have to actually earn to pay for it.

Doubling the cost is probably a good and easy method. Or, my preference would be to half my earning rate.

If you want to get into the details: I would not look at sales taxes, since whenever you spend that money (or the money plus interest from savings) you are still going to owe sales tax. Income tax, on the other hand, should drop to about zero if you retire early enough, so deferred income taxes (by way of 401k or IRA) would have a large effect. The formula I use to calculate the immediate earnings for deferred income taxes is 1/(1-state%+federal%)-1, or in your case 45.6%. Then you need to assume some level of annual return; this is really tough: some people prefer to use the historical CAGR for US stocks (~11%), some prefer to use a more conservative value as they expect valuations are currently high and the last 20 years haven't had great returns (say ~7%). Then you have to decide whether you want to consider the purchasing power of that money in the future, at which case you'll want to subtract the expected inflation rate from your expected return rate.

Regardless, if you aren't maxing out your tax-deferred savings, your future self is potentially missing out on a huge pot of money (and must continue working a lot longer than your current self might appreciate).