The only thing you'll need is a measuring tape.

Step1: Measure your abdomen at its thinnest point.
Enter abdomen here inches

Step 2: Measure your hips at their widest point.
Enter hips here inches

Step 3: Measure your neck just below your voice box.
Enter neck here inches

Step 4: enter your height to the nearest 1/4 inch here inches

Now Press Submit for your Body Fat %