How to Calculate Refining Value From an Assay Report

If you've ever sent scrap gold, silver, or platinum to be refined, you may have received an assay report. Report breakdown is important as it describes how to convert assay data to hard dollar value, which determines if you received a fair payout for the refining process.  This guide explains, in detail, how to calculate the refining value from an assay report.

What Is an Assay Report?

An assay report is a documentation a refiner creates after the melting, sampling, and testing of a batch to determine the amount of precious metals in the batch. Whether the material is jewelry scrap, other industrial byproducts, or bullion, an assay report is the foundation of any refining transaction. The assay report typically provides at least the gross weight, the assayed purity (fineness) of each metal, and the final content post-refining loss.

Since there can be significant financial implications, even from a few points, having the ability to correctly interpret an assay report can protect you from being paid less and help you negotiate better refining terms.

Key Components of an Assay Report

Most assay reports include the following elements:

Gross weight: the total weight of the material submitted, usually in troy ounces or grams

Fineness or purity: expressed as a percentage or in parts per thousand (e.g., 750/1000 for 18K gold)

Metal content breakdown: separate figures for gold, silver, platinum, or other metals if the lot is mixed

Return percentage: the portion of assayed metal the refiner agrees to pay you for, after accounting for processing losses

Market reference price: the spot price used as the benchmark for settlement, often tied to a specific date and time

All of these elements directly relate to the refining value. They should be checked against your records before any calculations are made.

How to Calculate Refining Value From a Gold Assay

The gold assay report will determine the quality of your sample based on purity as either karats or a decimal purity measurement. To figure out how many grams of pure gold you have, multiply the sample weight by the purity percentage. If one hundred grams of sample assayed at 91.6% pure (22K gold), then you have 91.6 grams of pure gold.

Next, you want to consider the refiner's Return. This is the loss the refiner will incur due to the smelting and chemical separation process. Let's say the refiner offers a 95% return on the 91.6 grams of pure gold. Now, your payable weight becomes about 87.02 grams. Finally, multiply that amount by the spot price of gold, as noted on your report, to determine your refining profit.

Gold Assay Formula:

Fine Gold Content = Gross Weight × Fineness
Payable Gold Weight = Fine Gold Content × Return %
Refining Payout = (Payable Gold Weight × Spot Price) − Fees

How to Calculate Refining Value From a Silver Assay

The math for a silver assay follows the same principles. However, silver is often more expensive to process and may earn less value when sold, meaning a silver refiner may take more deductions. Multiply the gross weight and assayed fineness and then apply the return percentage.

Silver assay results may vary from batch to batch. Therefore, it is more beneficial to request a batch breakdown to understand the refining value that each batch has earned rather than to accept a single, blended value. It allows one to see how their refiner arrived at a value.

Silver Assay Formula:

Fine Silver Content = Gross Weight × Fineness
Payable Silver Weight = Fine Silver Content × Return %
Refining Payout = (Payable Silver Weight × Spot Price) − Fees

How to Calculate Refining Value From a Platinum Assay

Platinum group metals (which may include palladium and rhodium) sometimes require separate line items. When calculating refining value from a platinum assay, isolate each metal's fine content individually, since spot prices and refiner return percentages typically differ across platinum, palladium, and rhodium even within the same lot.

Fine Platinum Content = GW(Pt) × F(Pt) Payable Platinum Weight = Fine Platinum Content × R(Pt) Platinum Payout = (Payable Platinum Weight × SP(Pt)) − Fees

Fine Palladium Content = GW(Pd) × F(Pd) Payable Palladium Weight = Fine Palladium Content × R(Pd) Palladium Payout = (Payable Palladium Weight × SP(Pd)) − Fees Total Refining Payout = Platinum Payout + Palladium Payout + (any additional PGM payouts)

Factors That Can Affect Your Final Refining Payout

Several variables beyond the raw assay numbers can influence what you ultimately receive:

• Timing of settlement: spot prices fluctuate, and some contracts lock in pricing at submission while others use payout-date pricing
• Minimum lot size requirements: smaller lots sometimes incur proportionally higher fees
• Refining fees and assay fees: flat or percentage-based charges that reduce your net payout
• Return percentage negotiated: larger or repeat clients often secure higher return rates
• Metal mix complexity: lots with multiple metals or heavy alloying may see lower returns due to processing difficulty

Calculating refining value from an assay is a method of ensuring that you are compensated for the material you submitted. Through the breakdown of an assay report, calculations relating to refining fineness and return percentage, and adjusting costs, a potential customer can assess if a refiner's offer is valid.

The math is the same for every assay, be it gold, silver, or platinum. So once you learn it, you're set.