Prong Setting Wire Calculator
Calculate prong wire gauge, length, and total wire for a prong setting from gem diameter, shape, and metal.
Returns 4-prong and 6-prong specs in inches and mm.
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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.