Round Pen Calculator ToolBy / Round Pen Calculator Round Pen Calculator Select Unit: Millimeters (mm) Inches Centimeters (cm) Feet Choose Input Type: Radius Diameter Enter Radius: Enter Diameter: Length of Each Panel: Width of Gate: Material Type: Wood Metal Plastic Calculate Area, Panels, and Fencing Length Note: Choose either Radius or Diameter for calculation. The result will be based on the selected unit.