I don't have an across I don't have an across-the-board material markup. When I first started working for myself, I did service work, and charged by the hour for labor + double retail for materials.
It didn't take long to figure out that doesn't work in a lot of scenarios.
I rarely charge T & M anymore, because most people want a firm price before I start. So I charge per opening on most of the stuff I do. I can give it to you short on new construction and remodel wiring.
New construction, my total price works out to about triple the cost of materials : 1 part material, 2 parts labor. I get there by charging $30 per opening for labor, then adding the materials cost for each type of opening.
Or you can simplify it by just charging $45 per opening across the board. Count every opening separately, including doorbell button + chime, garage door lo-vo, each 240v receptacle, hood, etc. Everything you run a wire to counts as an opening. Then count every breaker space as an opening. Then you don't add anything for the service.
That gets me in the "above average" price range for most homes.
For residential remodel, my total price is about 5x the cost of materials. I break down each opening a bit different, but similar concept