To really answer that question, I think you have to look at your overhead costs & don't confuse overhead with direct job costs.. Also, you need to decide if you will also be marking up your labor costs.
One overhead item frequently overlooked by small shops is all the time spent on "free" estimates. The big shops have full time estimators & that position is overhead, so if you're a one man shop like myself, you should figure your estimating time as overhead.
Once you know what your overhead is and how much you generally spend on material purchases, then you should have a realistic idea of what you need to charge.
In my area, my 25% markup is just a little on the low side of average. I usually lower the markup on really large $$ items.
Keep in mind that the markup is a percentage of the selling price and is not the multiplier. A 25% markup calls for a multiplier of 1.33
Tom
