How to measure racquet head
Take a piece of paper larger than the head of the racquet. Measure it and determine its area in cm (length x width). Weigh it on a small scale, in grams for ease of calculation but you can use the imperial system if you are a nostalgic. Divide weight by surface. Save the result. Draw the internal circumference of the head of the racquet. Cut out the oval and weigh it. Divide the result by the number saved previously. The result is the area in square centimeters (or whatever units you used). Simple enough.