I can't believe were having this conversation. Of course you have to measure your properties. How can you give a quality estimate without knowing your sq. footage. If not for the initial application but how about additional add-on services. How do you estimate a seed job, aeration any service this industry offers is based on know your job site. If your 10% over in usage your costing yourself money, especially as your business grows. If your using only 10 bags to complete a round, whats 1 bag. Not that much in dollars. Now your business has grown your treating 20 million sq ft all miss measured or not measured. Now your 10% could be a few hundred bags. What would be your lost revenue? Know your business, know your profits.