# Measuring and calculating in jewelry: gauge, sizes and metal weight

> Gauge, thickness, diameter, ring size, density and how to calculate the weight of a piece or the length of metal for a ring, with formulas and examples.

- Source: https://www.711grados.com/en/measuring-and-calculating-in-jewelry/
- Language: en
- Note: This entry was drafted with the help of AI and is pending review by the author.
- Published: 2026-09-07
- Updated: 2026-09-07
- Translation (es): https://www.711grados.com/es/medicion-y-calculo-en-joyeria/
- Author: Sandra Sánchez
- Site: 711 Grados (https://www.711grados.com/)

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Almost everything in jewelry is measured. These are the concepts and the sums used most at the bench.

## Vocabulary

- **Gauge (calibre):** a number that tells the thickness of sheet or wire. The American system (AWG or B&S) is the most used: the **higher** the number, the **thinner** the metal. Europe uses millimeters.
- **Thickness (espesor):** how thick a sheet is.
- **Diameter (diámetro):** the width of a circle or round wire.
- **Radius (radio):** half the diameter.
- **Circumference (circunferencia):** the perimeter of a circle, equal to π × diameter.
- **Ring size (talla de anillo):** the measurement of the inside of the ring. See [how to find your size](https://www.711grados.com/en/how-to-find-your-ring-size/) and [mandrels and sizers](https://www.711grados.com/en/mandrels-and-ring-sizers/).
- **Weight (peso), density (densidad), volume (volumen):** weight is volume multiplied by density.

## Gauges and millimeters

| AWG gauge | Millimeters |
| --- | ---: |
| 12 | 2.05 |
| 14 | 1.63 |
| 16 | 1.29 |
| 18 | 1.02 |
| 20 | 0.81 |
| 22 | 0.64 |
| 24 | 0.51 |

## Ring size conversion

| US size | Inside circumference (mm) | Inside diameter (mm) |
| --- | ---: | ---: |
| 6 | 51.9 | 16.5 |
| 7 | 54.4 | 17.3 |
| 8 | 57.0 | 18.2 |

European ISO sizes equal the inside circumference in millimeters. Other countries use their own numbers; always check the chart of whoever makes the ring.

## Length of metal for a ring

Length = π × (inside diameter + metal thickness). For a ring with a 17.3 mm inside diameter made from 2 mm strip: 3.1416 × 19.3 ≈ 60.6 mm.

## Weight of a piece

Weight (g) = volume (cm³) × density (g/cm³).

| Metal | Approximate density (g/cm³) |
| --- | ---: |
| Aluminum | 2.7 |
| Titanium | 4.5 |
| Stainless steel | 7.9 |
| Brass | 8.4 to 8.7 |
| Copper | 8.96 |
| Sterling silver 925 | 10.36 |
| 14-karat gold | 12.9 to 13.6 |
| 18-karat gold | 15.2 to 15.9 |
| Pure gold | 19.32 |
| Platinum | 21.45 |

**Example:** a round wire 2 mm in diameter and 60 mm long has a volume of π × 1² × 60 ≈ 188 mm³ = 0.188 cm³. In sterling silver it weighs 0.188 × 10.36 ≈ **1.95 g**; in 18-karat gold, about **2.9 g**.

## Alloy percentage

An 18-karat alloy is 75% gold. To make 100 g you need 75 g of pure gold and 25 g of other metals (copper, silver…). See [alloys](https://www.711grados.com/en/jewelry-alloys-how-they-are-made/).

## Measuring accurately

A [caliper and a scale](https://www.711grados.com/en/jewelers-scale-and-caliper/) reading tenths of a gram are enough to start.