# Classes of Domes

When using a geodesic dome calculator it does all the math for you. But what’s really behind those results? This page is a summary of mathematical classes used in geodesic designs.

Icosahedron/Alternate (class I) |
Octahedron/Triacon (class II) |
Tetrahedron (class III) |

All subdivisions of class I, II and III are based on the polyhedron.

**Class I** **(a.k.a Alternate**) is the most common subdivision used these days. Almost all geodesic calculators on the web are based on this class.

**Class II** (**Octahedron/Triacon**) was originally the subdivision type used in the early days of geodesics, the one Buckminster Fuller the father of geodesics primarily used. You will find references to this subdivision class in books such as Domebook 1 and Domebook 2.

**Class III ( Tetrahedron)** is rarely used in designing geodesic domes.

**What is important to remember**

For most who wish to build their own geodesic dome, class I is almost exclusively used with geodesic dome calculators.