Concentrate Grade Calculator

Work out concentrate grade instantly with clear inputs, formula shown and shareable results.

About Concentrate Grade Calculator

Concentrate is assayed and paid on a dry basis, so wet tonnage must be converted first. Smelters then apply a unit deduction — commonly 1 unit for copper concentrate, 8-9 units for zinc — before paying, so the payable grade is always below the assayed grade.

Formulas

Concentrate grade

Dry tonnes = wet tonnes x (1 - moisture); grade % = metal x 100 / dry tonnes

Payable metal

Payable metal = dry tonnes x (grade - unit deduction) / 100

Worked example

With the default values below, Concentrate Grade Calculator returns Concentrate Grade (dry basis) of 30.4348%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Metal In Concentrateminimum 0 tonnes: 280 tonnes
Concentrate Tonnageminimum 0 tonnes: 1,000 tonnes
Moisture Contentaccepts 0–40 %: 8 %
Smelter Payable Deductionaccepts 0–20 % units: 3 % units

Results

Concentrate Grade (dry basis): 30.4348%
Dry Concentrate Tonnage: 920.00
Payable Grade After Deduction: 27.4348%
Payable Metal: 252.400

Step by step

1Values used
2Concentrate grade
3Payable metal
4Concentrate Grade (dry basis)= 30.4348
5Dry Concentrate Tonnage= 920.00
6Payable Grade After Deduction= 27.4348
7Payable Metal= 252.400

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why do smelters deduct units?

It represents unrecoverable metal in slag and a commercial risk-sharing convention. Combined with treatment and refining charges, deductions determine the net smelter return the mine actually receives.

Is higher concentrate grade always better?

Usually — it reduces freight, treatment charges and deduction losses per unit of metal. But pushing grade too high normally costs recovery, and the optimum is a grade-recovery trade-off.