What is the mathematical relationship between g/t, ppm, and percentage?

One gram per metric tonne (1 g/t) is equivalent to 1 part per million (ppm) by mass, because one metric tonne equals 1,000,000 grams. One mass percent (1%) represents 10,000 ppm or 10,000 g/t.

What is the difference between oz/t and oz/st?

oz/t denotes troy ounces per metric tonne (1,000 kg), where 1 oz/t = 31.10348 g/t. oz/st denotes troy ounces per short ton (2,000 lbs or 907.18474 kg), where 1 oz/st = 34.28571 g/t. Always verify which ton convention a source uses before comparing grades.

Does contained metal account for mill recovery or mining dilution?

No. Theoretical contained metal reflects the total insitu mass of target element present (Ore Mass × Grade). Actual recovered metal will be lower due to mining dilution, ore loss, and metallurgical recovery efficiency.

What conversion constant is used for troy ounces?

In accordance with international metrology standards (NIST SP 811), 1 troy ounce (ozt) is defined as exactly 31.1034768 grams, distinct from the avoirdupois ounce (28.34952 grams).

Ore Grade Calculator

Calculate ore assay grades across metric and imperial mining units, or compute theoretical contained metal mass from ore tonnage and grade.

Sample Assay Parameters

Measured / Contained Metal Mass

Total Ore Sample Mass

Calculation Results Assay Grade

Enter inputs and select Calculate

Unit Relationships and Evaluation Limitations

Standard Unit Equivalents

• 1 g/t = 1 ppm = 0.0001% (10,000 g/t = 1%)
• 1 troy ounce = 31.1034768 g (NIST SP 811)
• 1 metric tonne (t) = 1,000 kg = 2,204.6226 lbs
• 1 short ton (st) = 907.18474 kg = 2,000 lbs
• 1 oz/st (opt) = 34.28571 g/t (ppm)
• 1 oz/t = 31.10348 g/t (ppm)

Important Metallurgical Caveats

• Theoretical Insitu vs Recoverable: Contained metal calculations calculate total chemical mass in place, excluding metallurgical recovery efficiency and smelting deductions.
• Dilution and Mining Loss: Bulk mining introduces barren wall rock (dilution) lowering delivered mill head grade compared to undiluted drill core assays.
• Dry vs Wet Basis: Ore tonnage and grade must be evaluated on consistent dry metric bases to avoid moisture weight distortion.

Copied!

Summary

Calculate ore assay grades across metric and imperial mining units, or compute theoretical contained metal mass from ore tonnage and grade.

How it works

Select the calculation workflow: "Assay Grade from Sample" or "Contained Metal from Tonnage".
In Assay Grade mode: enter the measured metal mass (mg, g, kg, or troy oz) and total ore sample mass (g, kg, metric tonne, or short ton).
In Contained Metal mode: enter the bulk ore tonnage (metric tonne, short ton, or kg) and the known ore grade (g/t, ppm, %, oz/metric tonne, or oz/short ton).
Click Calculate to compute grade equivalents or total contained metal mass.
Use Reset or modify any input to refresh the calculation.

Use cases

Converting drill core or grab sample assay measurements into reporting units.
Converting between metric (g/t, oz/metric tonne) and North American (oz/short ton) mining standards.
Estimating theoretical contained metal in an ore block, stockwork, or processing stockpile.
Cross-checking fire-assay laboratory reports and portable XRF field results.
Evaluating insitu resource estimates prior to applying metallurgical recovery or mining dilution factors.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu