Introduction. This professional converter implements the legally exact relationship between pennyweight and grams from the troy-weight system. It is crafted for jewelers, refiners, pawnbrokers, and auditors who demand repeatable accuracy and transparent methodology.
Authoritative Data Source & Methodology
Primary authority: NIST Office of Weights and Measures, “Conversion Factors for Precious Metal Sales (rev. March 2015)”. Exact definition: 1 troy ounce = 31.1034768 g and 1 troy ounce = 20 dwt, therefore 1 dwt = 31.1034768 / 20 = 1.55517384 g (exact). Source: NIST documents EPO5 tables and OWM guidance.
All calculations in this tool strictly apply those definitions.
- NIST table (troy oz ↔ grams): confirms
31.1034768 gper troy ounce. - NIST pennyweight table: confirms
1 dwt = 1.55517384 gexactly. - Background: Troy weight and Pennyweight entries describe usage and history in precious-metal trade.
“Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.”
References: NIST EPO5 Ounces (troy) to Grams; NIST Pennyweight to Grams; Wikipedia “Troy weight” and “Pennyweight”; MGS Refining conversion/chart; Seattle Findings DWT-OZ-GRAMS chart.
The Formula Explained
\( 1~\mathrm{dwt} = \frac{1}{20}~\mathrm{ozt} \quad\) and \( \quad 1~\mathrm{ozt} = 31.1034768~\mathrm{g} \)
Therefore:
\( \displaystyle 1~\mathrm{dwt} = \frac{31.1034768}{20}~\mathrm{g} = 1.55517384~\mathrm{g} \)
Direct conversions:
\( \displaystyle g = \mathrm{dwt} \times 1.55517384 \quad\) and \( \quad \mathrm{dwt} = \frac{g}{1.55517384} \)
Glossary of Variables
| Symbol / Field | Meaning | Units |
|---|---|---|
dwt (Pennyweight) | Troy mass used for precious metals; 20 dwt = 1 troy ounce | dwt |
g (Grams) | SI mass unit | g |
k (Exact factor) | Conversion constant from dwt to g | k = 1.55517384 |
How It Works: A Step-by-Step Example
Goal: Convert 7.5 dwt to grams.
- Choose “dwt → g”.
- Enter
7.5in the Pennyweight field. - Apply the exact formula \( g = \mathrm{dwt} \times 1.55517384 \).
- Compute: \( 7.5 \times 1.55517384 = 11.6638038 \,\mathrm{g} \).
- Rounded to four decimals: 11.6638 g.
Frequently Asked Questions (FAQ)
Is the dwt↔g conversion factor exact?
Yes. It is derived from exact definitions in the troy-weight system mandated by standards bodies (NIST). No rounding is applied to the factor itself.
Why use pennyweight instead of grams?
Pennyweight is traditional in precious-metal trade because values are neatly related to the troy ounce (20 dwt = 1 ozt), which is often quoted in markets.
Does this work for avoirdupois ounces?
No. Avoirdupois ounces are used for everyday goods and are a different system; the converter targets the troy system used for bullion and jewelry.
How many dwt are in 5 grams?
\( \mathrm{dwt} = \frac{5}{1.55517384} \approx 3.21507 \,\mathrm{dwt} \).
What level of precision do you display?
Internally the tool uses full precision of the factor. Results are shown with up to 8 significant digits (configurable) to balance readability and accuracy.
Where can I verify these numbers?
Check NIST OWM conversion tables for troy units and grams, or the “Troy weight / Pennyweight” encyclopedic references for historical context.