Convert the developer's fee percentage into decimal format. For example, if the fee is 5 percent, you would have a percentage of .05.
Calculate the total cost of the project. This includes all labor, the cost of the land, materials and time. If you are unsure, consult the developer.
Multiply the total cost of development by the percentage in decimal form. For example, if the cost of development is $500,000 and the developer's fee is 5 percent, your equation would be 500,000 x .05.
Double-check your multiplication. The result of multiplying the total cost of development by the percentage in decimal form is the developer's fee in dollars. For example, 500,000 x .05 = 25,000. The developer's fee is $25,000.