The research desk · weight, not worth
Find the fine weight.
Gross weight is the whole alloy. Fine weight is the portion attributable to the precious metal you specify.
Check which weight you have.
Use the gross weight of the metal alloy, excluding packaging, stones and other non-alloy parts. Supply its stated fineness in parts per thousand: the proportion of that alloy represented by the specified precious metal. The tool does not infer either value.
If a specification is already fine weight, do not apply purity again. This converter starts with gross weight only. Confirm the weight basis and unit with the source before using it; a troy ounce is not an ordinary (avoirdupois) ounce.
A fineness entry is not an assay, proof of authenticity or proof of IRA eligibility. The result is conditional arithmetic based on your inputs, not measured or independently verified metal content.
Your figures · no preset purity
Gross → fine
Leave missing figures blank: unknown is not zero. Use positive decimal numbers with a decimal point, not commas, signs or exponent notation. Changing the unit reinterprets the entered number; it does not convert the input for you.
Calculated fine-metal content
Unknown — enter gross weight and fineness to calculate.
- Fine-metal grams (g)
- Fine-metal troy ounces (ozt)
Your calculation, step by step
Workings appear when inputs are complete. Intermediate displays are rounded; the calculation uses unrounded values. ≈ means approximately equal.
Results are rounded to at most 12 significant digits, not a claim of measurement accuracy. Very small or large results may use scientific notation. Inputs or results outside the browser’s normal finite numeric range are rejected rather than shown as zero or infinity.
Browser-only worksheet: these inputs are not sent over the network or saved by this tool. It uses no local or session storage. Reset clears this form, not your downloads. A downloaded text record, printout or PDF remains your separate, unencrypted copy. Downloads include the current weight, fineness, results, workings and source context; no account or automatic saving is added.
The calculation, on paper.
- Gross grams = gross weight in grams, or gross troy ounces × 31.1034768.
- Fine-metal grams = gross grams × (fineness ÷ 1000).
- Fine-metal troy ounces = fine-metal grams ÷ 31.1034768.
Use the same metal and weight basis throughout. Missing gross weight or missing fineness means the result remains unknown. The number 1000 is the denominator for parts per thousand, not an assumed purity.
Gross alloy weight & unit: __________________________
Stated fineness & document reference: __________________________
Fine-metal grams: ______________ Fine-metal troy ounces: ______________
Sources & limits
- NIST Handbook 44 (2026), Appendix C — General Tables of Units of Measurement (PDF), page C-19: the troy-ounce row gives 31.103 476 8 grams. This worksheet uses 31.1034768 grams per troy ounce as its fixed conversion.
- British Hallmarking Council / GOV.UK — Hallmarking is the law: guidance summary, “A metal and purity (fineness) mark”: precious-metal content is recorded in parts per thousand, expressing its proportion in the alloy. This citation explains the term; it does not authenticate your entry.
Source-content check: . The cited bodies were retrieved and the relevant passages checked; this is not professional financial review or independent testing of any item. Editorial edition: 23 September 2026. Worksheet interaction update: ; this is not a new source-review date. No professional financial review has been completed.
Next: read the bullion buying notes or request a written specification. Keep the original weight and fineness evidence beside your calculation.