The (my) percentage varies based on the ratio of material dollars/labor dollars. So I use an overall markup on both material and labor.
I look at margin dollars per man/hr.
This is on major commercial construction. Not service or resi.
Over the years we noticed the trades that marked up material an average of 50% or more are still in business and growing, you can play with tables and charts till the cows come home and the end result will still be you need a profit on material to keep the doors open.
Equipment and fixtures are another issue, they need to be priced with care to find the price sweet spot.