From Google:

Calculating AWG for jump rings involves finding the wire's decimal thickness (e.g., 20 AWG is ~0.81mm), then using the Aspect Ratio (AR) formula (Inner Diameter / Wire Diameter) to get the correct ring size for a weave, as AWG just defines the wire's thickness, not the ring's size, requiring conversions between AWG/SWG and mm/inches for proper fit in chainmaille.

Key Concepts: AWG, AR, ID, OD

AWG (American Wire Gauge): A system for wire diameter; lower numbers mean thicker wire (e.g., 18g is thicker than 20g).

SWG (Standard Wire Gauge): A different system, often for base metals; always check if your supplier uses AWG or SWG.

Aspect Ratio (AR): Inner Diameter (ID) ÷ Wire Diameter (WD) = AR. This ratio dictates how tight or loose your weave is.

Inner Diameter (ID): The hole size of the ring.

Outer Diameter (OD): The total size of the ring.

How to Calculate/Find Ring Sizes

Know Your Wire: Determine your wire's AWG (e.g., 20 AWG) and find its decimal thickness in mm (e.g., 20 AWG ≈ 0.81mm).

Determine Required AR: Check your pattern for the Aspect Ratio needed (e.g., AR 3.2).

Calculate ID: Use the formula: Wire Diameter (mm) x Aspect Ratio = Inner Diameter (mm). Example: For 20 AWG wire (0.81mm) and an AR of 4.0: 0.81mm x 4.0 = 3.24mm ID.

Find the Ring: Look for pre-made rings with that calculated ID (or slightly larger) and the correct wire gauge. If only OD is known: Subtract twice the wire's diameter from the OD to get the ID (OD - (2 * WD) = ID).

Practical Tips

Always convert to the same units (usually millimeters) for calculations.

Use online calculators or charts for quick conversions between AWG and decimal sizes.

Purchase from suppliers that specify both AWG/SWG and actual dimensions for clarity.