Prong Setting Wire Calculator
Calculate wire gauge, length, and dimensions for prong settings based on gemstone size, shape, and metal type.
Prong settings explained:
A prong (or claw) setting uses metal tabs bent over the girdle of a gemstone to hold it in place. The number, thickness, and height of prongs must match the stone size and shape. Too-thin prongs bend and lose stones. Too-thick prongs obscure the stone and look clunky.
Prong count by stone shape:
| Stone Shape | Minimum Prongs | Recommended | Notes |
|---|---|---|---|
| Round | 4 | 4–6 | 6 prongs for stones over 1 carat |
| Oval | 4 | 4–6 | Place at compass points |
| Princess (square) | 4 | 4 | V-prongs protect corners |
| Marquise | 6 | 6 | V-prongs on pointed ends |
| Pear | 5 | 5–6 | V-prong on point, round prongs elsewhere |
| Emerald cut | 4 | 4 | Corner prongs standard |
| Heart | 5 | 5–6 | V-prong on point, 3 prongs on lobes |
Wire gauge selection formula:
The prong wire must be thick enough to hold the stone securely but thin enough to push over the girdle with a prong pusher:
Minimum wire diameter (mm) = Stone diameter (mm) × 0.08 + 0.3
Recommended wire gauge = Round to nearest standard gauge
| Stone Diameter | Min Wire Dia | Recommended Gauge |
|---|---|---|
| 3 mm | 0.54 mm | 24 ga (0.51 mm) |
| 4 mm | 0.62 mm | 22 ga (0.64 mm) |
| 5 mm | 0.70 mm | 21 ga (0.72 mm) |
| 6 mm | 0.78 mm | 20 ga (0.81 mm) |
| 8 mm | 0.94 mm | 19 ga (0.91 mm) |
| 10 mm | 1.10 mm | 18 ga (1.02 mm) |
| 12 mm+ | 1.26 mm+ | 16 ga (1.29 mm) |
Prong height formula:
Prong height = Stone depth + 1.5 mm (for girdle grip) + Seat depth (0.5–1 mm)
Total wire length per prong:
Wire per prong = Prong height + Base attachment length (3–5 mm)
Total wire = Wire per prong × Number of prongs × 1.15 (waste factor)
Example for a 6 mm round stone:
- Stone depth: 3.8 mm
- Prong height: 3.8 + 1.5 + 0.75 = 6.05 mm
- Wire per prong: 6.05 + 4 = 10.05 mm
- 4 prongs × 10.05 × 1.15 = 46.2 mm total wire
- Wire gauge: 20 ga (0.81 mm)
Metal considerations:
Sterling silver prongs wear faster than gold and need thicker wire (go up one gauge). Platinum prongs are the most secure but require specialized tools. Gold-filled wire should not be used for prongs as the base metal can be exposed during filing.