Lay a string on the ground next to one side of the mobile home.
Stretch the string to the other end of the mobile home. Make sure the string is laying flat on the ground, and not over any plants or curled up with knots. If the mobile home sits on a hill, you will need to hold the string at the bottom of the mobile home and pull tight. If you let the string hang down you will not get an accurate measurement.
Cut or mark the string where the beginning and end points of the mobile home are.
Stretch the string out on a flat surface, like the road.
Measure the length of this string with a yard stick, tape measure or ruler. You will have to reposition the measuring device on the string so remember where you left off. Write this number down
Repeat Steps 1-5 for the other end of the mobile home. You should now have two different measurements. If you have any protruding elements on the mobile home repeat Steps 1-5 for each element.
Multiply the two numbers together. This is the square footage of the mobile home. Multiply any other measurements and add those numbers to the other numbers to get the exact square footage of the mobile home.