# Weights

## Relative Weights

Formula to calculate metal weight and cost from wax models:

• Wax weight (dwt.*) x specific gravity of desired metal** = weight of casting in dwt. x Cost/dwt. + Labor Charges = Cost of Casting.
• Allow some additional weight for the remaining gate.

The top line is the known material (in pennyweights). The first column is the desired material. For example, if you have a wax that weighs .7 dwt, and you want to know its corresponding weight in platinum, go down the wax column to platinum and multiply .7 dwt. (wax weight) by 21.45. 15.02 dwt’s is the corresponding weight in platinum.

 Wax Sterling 10Y 14Y 18Y 14W 18W Platinum Sterling 10.36 1.00 0.90 0.79 0.67 0.82 0.71 0.49 10Y 11.60 1.11 1.00 0.89 0.74 0.92 0.79 0.54 14Y 13.08 1.27 1.13 1.00 0.84 1.03 0.89 0.61 18Y 15.60 1.49 1.34 1.19 1.00 1.23 1.06 0.73 14W 12.65 1.22 1.09 0.97 0.81 1.00 0.86 0.59 18W 14.65 1.41 1.26 1.12 0.94 1.16 1.00 0.68 PT 21.45 2.04 1.85 1.64 1.38 1.70 1.46 1.00

*The specific gravity of wax is 1. **See Specific Gravity Chart or Relative Weights.

### Weight Conversion

To convert:
Pennyweights to grams Multiply by 1.55518
Grams to pennyweights Multiply by 0.64301
Ounces troy to grams Multiply by 31.1035
Grams to ounces troy Multiply by 0.0321507
Ounces avoirdupois to grams Multiply by 28.3495
Grams to ounces avoirdupois Multiply by 0.0352740
Ounces troy to ounces avoirdupois Multiply by 1.09714
Ounces avoirdupois to ounces troy Multiply by 0.911458
Pounds avoirdupois to kilograms Multiply by 0.4535924
Kilograms to pounds avoirdupois Multiply by 2.20462
Kilograms to ounces avoirdupois Multiply by 35.2740
Kilograms to ounces troy Multiply by 32.1507

### Avoirdupois Weight

Used in Weighing Precious and Semi-Precious Stones Used in Weighing the Base Metals
1 carat = 0.20 grams 16 ounces = 1 pound
1 gram = 5 carats 16 ounces = 7000 grains
1 carat = 3.086 grains troy The avoirdupois pound is about 21.5% heavier than the troy pound
1 carat = 0.007 ounce avoirdupois
1 carat = 100 points 28.35 grams = 1 ounce avoirdupois

### Troy Weight

Used in Weighing the Precious Metals
24 grains 1 pennyweight
20 pennyweights (dwt.) 1 ounce troy
12 ounces 1 pound troy
5760 grains 1 pound troy
The troy ounce is about 10% heavier than the avoirdupois ounce.
31.1035 grams 1 ounce troy
1 gram 15.432 grains troy
1.555 grams 1 pennyweight (dwt.)