Select the chart title and use the dropdown to select between charting Gear Inches, Development, or Speed.  Internally geared hubs are selected from a database, external gears are entered manually.  To specify a combination IGH/external hub like the SRAM DualDrive or Sturmey Archer CS-RF3, select the IGH on the “Rear or Mid IGH” line and select “External” for the “Rear” line.  Areas where data can be entered are in yellow.  See Glossary of Terms for a description of some of the terms used in the calculator.