Contractor Draws / Percentage work completed

[Andrew Lawrence]

When giving out draws to contractors (30/30/30/10), how do you determine, based on pictures what percentage of the work is actually complete? As in, the contractor has started his first 1/3 of work, calls/texts you and says he's ready for another draw, sends you pictures of completed work. Coming from someone with minimal construction knowledge or experience, how do you gauge that a project is a certain percentage complete? Ex. I can see the granite countertops are done, but based on the whole project, what percentage does that equate to?