---
title: "STEP file: meaning in gemology"
description: "STEP is a standard CAD format that stores an exact solid, with each facet as a true plane. CAD programs such as FreeCAD, Rhino and Fusion open it to measure…"
url: https://digitalgemology.com/learn/glossary/step-file
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Cutting and files

# STEP file

Also called STEP, .stp

STEP is a standard CAD format that stores an exact solid, with each facet as a true plane. CAD programs such as FreeCAD, Rhino and Fusion open it to measure a stone and design a setting.

## In more detail

STEP keeps exact geometry, while mesh formats approximate it with triangles. A turned girdle can be one cylinder in a STEP solid.

## How we measure it

Our facet counts come from the planar faces of each STEP solid. We check every STEP file with the Open CASCADE kernel. Our tools read a STEP cylinder as a ring of flat facets with the same cross-section area.

## Related terms

- [3D model](https://digitalgemology.com/learn/glossary/3d-model): A 3D model of a gemstone is a digital solid of its facets for CAD, rendering, printing or games. An exact model has flat facets, sharp edges and a closed, watertight surface at real size.
- [Mesh](https://digitalgemology.com/learn/glossary/mesh): A mesh describes a 3D surface as many small flat triangles joined at their edges. STL, OBJ, FBX and GLB files store a mesh.
- [Facet count](https://digitalgemology.com/learn/glossary/facet-count): The facet count is the number of facets on a cut. On our cut pages, it is the number of planar faces of the cut's STEP solid.
- [Turned girdle](https://digitalgemology.com/learn/glossary/turned-girdle): A turned girdle is a girdle with a smooth round edge, shaped as a cylinder, instead of flat girdle facets. CAD often gives a round stone this kind of girdle.

## Learn more

- [Who uses our files](https://digitalgemology.com/about/files)
- [The 3D models](https://digitalgemology.com/about/how-we-measure/3d-models)
- [Your own file](https://digitalgemology.com/about/how-we-measure/your-own-file)

[All 328 terms](https://digitalgemology.com/learn/glossary)