Topology Explorer

Explore Euler characteristics, surfaces, Möbius strips, and knots.

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Topological Surfaces & Manifolds. Browse the library of standard surfaces on the right.

Select a knot to visualize:

χ = V−E+F —
Surface —
Genus g —
Betti numbers —
Euler's Formula for Polyhedra
For any convex polyhedron: χ = V − E + F = 2
For a surface of genus g (g handles): χ = 2 − 2g
Sphere: χ=2 (g=0) | Torus: χ=0 (g=1) | Double-torus: χ=−2 (g=2)
Shape V E F χ
Tetrahedron4642
Cube81262
Octahedron61282
Torus1210
Klein Bottle1210
Sides 1
Edges 1
Orientable? No
χ 0