This sounds way too low, and also varies a lot state-to-state. I just looked up 2020. Your Federal and FICA on 100k are about 23k. If you max out a 401(k) you can drop that to about 18.5k.

If you are in California, say, add about 5500 without 401(k), 4k with so total income tax is 29k, or 22k maxing out tax deferral.

So effective rate is about double what you quote, at least for single filing.