There are quite a few projects for which you might want to charge by the job by using square feet. Some of these jobs include painting, building and lawn services. If you are going to charge by the job instead of by the hour, a price that covers your expenses and labor and is still fair to the customer can help you to gain business.
Establish your cost of materials and supplies per square foot. You may have to do some division to calculate this. For instance, one basic material that you would need for a painting job is the paint. If you know that it takes $50 in paint to paint a room that is 100 feet square, divide 50 by 100 to get a price of 50 cents per square foot just for the paint. Add the cost of all supplies related to the job, as well as any maintenance costs that you might have to spend in order to keep up your equipment.
Estimate how many hours it would take you to do a specific job. For instance, you may figure that it would take you four hours to paint a room that is 100 square feet. You also might decide that your labor is worth $30 per hour, which means that the job would cost $120 in terms of labor.
Divide your calculation by the square footage of the job to determine the cost of labor per square foot. For example, if the job would cost $120 in labor, and the square footage is 100, divide 120 by 100 to get a cost of $1.20 per square foot.
Add your labor calculation to your materials and supplies calculation to determine the overall price to charge per square foot.
Call other professionals in your area who are doing the same type of work and ask them about their prices per square foot. You'll want your price to be similar in order to be competitive, so you may have to adjust your fees if necessary.