Include the costs the job actually consumes
Materials and field labor are only the obvious part. Include payroll burden, takedown labor, consumables, fuel, equipment wear, callbacks, selling time, and a defensible share of overhead. A margin calculator cannot rescue an incomplete cost estimate.
Margin is not markup
A 40% margin on $1,400 of cost requires a selling price of $2,333.33. That is a 66.67% markup on cost. Confusing those percentages can leave a meaningful gap.