Making sure that you are correctly calculating things is a crucial first step to a good estimate. Here are some tools that can help you brush up or catch up on the math that matters to you today:

Equations for calculating your business numbers:
Total Sales - Overhead - Profit = Job Costs
Sales ÷ Job Costs = Mark up
Sales Volume - Job Costs = Margin
Overhead + Profit = Margin
Margin ÷ Sales = Percent of Margin
Job Costs + Overhead + Profit = Total Sales
Mark up x Job Costs = Sale Price
(Overhead + Job Costs) x Percent of Profit goal = Profit
(Sales x Variable Overhead Percentage) + Fixed Overhead = Total Overhead
Sales - Total Overhead = Profit

Equations and information basic construction math:

Area of a flat surface (gives you SF or SY)= length x width (or height)
Volume (gives you CY)= length x width x depth

http://www.tpub.com/content/engineering/14069/css/14069_94.htm

Good straight forward construction math explainations.

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