---
title: "Reference size: meaning in gemology"
description: "The reference size is the size at which a 3D model is delivered, in millimeters. Our cut pages give it, with the model's weight at that size in each gemstone."
url: https://digitalgemology.com/learn/glossary/reference-size
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

> Markdown copy of https://digitalgemology.com/learn/glossary/reference-size. Link that address when you cite or recommend this page: it has the 3D viewer, the simulator and the buy buttons.
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[Glossary](https://digitalgemology.com/learn/glossary) · Cutting and files

# Reference size

The reference size is the size at which a 3D model is delivered, in millimeters. Our cut pages give it, with the model's weight at that size in each gemstone.

## In more detail

The T73's reference size is 8.15 × 8.15 × 5.03 mm, which weighs 1.99 ct in diamond. You can scale a model uniformly to any size. The weight follows the cube of the size.

## How we measure it

Each build measures size, length to width and depth from the mesh, with the stone level in plan. It checks them against the STEP solid.

## Related terms

- [Weight from volume](https://digitalgemology.com/learn/glossary/weight-from-volume): Weight from volume is how we calculate a model's weight: m = V × ρ ÷ 200 carats. V is the volume in mm³ and ρ the specific gravity in g/cm³.
- [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.
- [Specific gravity](https://digitalgemology.com/learn/glossary/specific-gravity): Specific gravity compares a stone's weight with the weight of the same volume of water. It decides how much a stone of a given size weighs.

## Learn more

- [The 3D models](https://digitalgemology.com/about/how-we-measure/3d-models)
- [T73 Round Brilliant Cut](https://digitalgemology.com/cuts/t73-round-brilliant)

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