BIPM-ratified constants · v1.0

Converter

Uk, assay ton to kilogram converter calculator.

Convert UK assay tons to kilograms using the exact factor 98/3000 (0.032667). Ideal for fire assay labs, mining engineers, and precious metals analysts.

From

at_to_kg

1 at_to_kg =0.032667Kilograms

Equivalents

Precision: 6 dp · Notation: Decimal · 2 units

Assay Tons → Kilograms

UKat_to_kg0.032667

→ UK Assay Tons

Kilogramskg_to_at30.6122

Common pairings

1 at_to_kgequals30.6122 kg_to_at

1 kg_to_atequals0.032667 at_to_kg

The conversion

How the value
is computed.

UK Assay Ton to Kilogram Conversion: Formula, Derivation, and Applications

The UK assay ton is a specialized unit of mass used almost exclusively in fire assay testing of precious metals. One UK assay ton equals exactly 98/3 grams (the repeating decimal 32.666... g, or approximately 32.667 grams), which converts to 0.032667 kilograms. This unit is deliberately sized so that the number of milligrams of precious metal recovered per assay ton charge numerically equals the troy ounces of that metal per long ton of ore — a calculation convenience deeply embedded in British and Commonwealth mining practice.

The Conversion Formula

The standard formula for converting UK assay tons to kilograms is:

m(kg) = m(AT_UK) × 0.032666... (6 repeating)

Where m(kg) is the equivalent mass in kilograms and m(AT_UK) is the mass expressed in UK assay tons. The exact rational value of the conversion factor is 98/3000 (equivalently 49/1500). To reverse the conversion — expressing kilograms as UK assay tons — divide by the same factor, which is equivalent to multiplying by 3000/98 ≈ 30.6122.

Derivation of the Conversion Factor

The assay ton's precise value is rooted in the relationship between troy weight and avoirdupois weight within the imperial long-ton system. One UK long ton equals 2,240 avoirdupois pounds, or approximately 1,016,046.9 grams. One troy ounce equals 31.1034768 grams. A long ton therefore contains approximately 32,666.7 troy ounces (1,016,046.9 ÷ 31.1035 ≈ 32,666.7).

The UK assay ton is defined so that 1 milligram of precious metal recovered per assay ton charge corresponds to 1 troy ounce per long ton of ore. Setting the assay ton mass a to satisfy 1 mg/a = 1 troy oz/long ton yields:

a = 1,016,046,900 mg ÷ 32,666.7 ≈ 32,666.7 mg = 32.667 g = 0.032667 kg

This derivation is consistent with conversion factors published in the NIST Guide for the Use of the International System of Units (SI) — NIST SP 811, and formally documented in the California Code of Regulations Title 4, Division 9, which defines assay tons for commercial weights and measures compliance.

Variables Defined

Value to Convert (value): The numeric mass entered by the user. By default this represents a quantity in UK assay tons; when the conversion direction is reversed, it represents kilograms.
Conversion Direction (direction): Selects whether the tool converts UK assay tons to kilograms or kilograms back to UK assay tons. Reversing direction applies the reciprocal factor 3000/98 (≈ 30.6122).

Worked Examples

Example 1 — UK Assay Tons to Kilograms: A fire assay laboratory prepares a charge of 5 UK assay tons. The equivalent mass in kilograms is: 5 × 0.032667 = 0.16333 kg (163.33 g).

Example 2 — Kilograms to UK Assay Tons: A metallurgist records a refined sample of 2.5 kg and needs to report in UK assay tons: 2.5 ÷ 0.032667 = 76.53 UK assay tons.

Example 3 — Ore Grade Context: When an assay charge of exactly 1 UK assay ton yields 6.2 mg of gold, the deposit grade is reported directly as 6.2 troy oz of gold per long ton of ore. This direct numerical equivalence is the primary engineering rationale for the assay ton unit, eliminating a conversion step in every grade calculation.

Industrial and Laboratory Applications

The UK assay ton appears in several specialized contexts:

Fire assay laboratories processing gold, silver, and platinum group metals (PGMs) from British and Commonwealth mining operations.
Ore grade reporting where legacy contracts specify grades in troy ounces per long ton.
Bullion customs and export documentation governed by imperial-system commercial terms.
Historical metallurgical research comparing pre-metric assay records with modern SI datasets.

Modern SI-compliant reporting increasingly uses grams per metric ton (g/t), but conversion to and from UK assay tons remains essential for interoperability with legacy datasets, older regulatory frameworks, and international trade documentation referencing long-ton grades.

Reference

Frequently asked questions

What is a UK assay ton and how is it defined?

A UK assay ton is a specialized unit of mass equal to exactly 98/3 grams (approximately 32.667 grams or 0.032667 kilograms). It is sized so that milligrams of precious metal recovered per assay ton charge numerically equal the troy ounces of that metal per UK long ton of ore, simplifying fire assay grade calculations in British and Commonwealth mining operations.

What is the exact conversion factor from UK assay tons to kilograms?

The exact conversion factor is 98/3000, equal to the repeating decimal 0.032666... (6 repeating), or approximately 0.032667 kg per UK assay ton. This means 1 UK assay ton equals 32.667 grams or 0.032667 kg. The factor is derived from the definition of the UK long ton (2,240 lb) and the troy ounce (31.1035 g), both foundational to the imperial precious metals system.

How does the UK assay ton differ from the US assay ton?

The UK assay ton (32.667 g) is based on the imperial long ton of 2,240 pounds, while the US assay ton (29.167 g) is based on the US short ton of 2,000 pounds. Both units link milligrams per assay ton charge to troy ounces per their respective ton, but they produce different numeric grade values for the same ore sample, making unit specification critical in cross-border reporting and international mine valuations.

Why do precious metals laboratories use assay tons instead of grams or kilograms?

Assay tons eliminate a conversion step in grade calculations. When a laboratory weighs out exactly 1 UK assay ton (32.667 g) and recovers X milligrams of gold, the deposit grade is reported directly as X troy ounces per long ton — no additional arithmetic required. This built-in proportionality speeds up high-volume fire assay workflows and reduces transcription errors across thousands of daily grade calculations in active mining operations.

How do you manually convert UK assay tons to kilograms without a calculator?

Multiply the number of UK assay tons by 0.032667. For example, 10 UK assay tons equals 10 x 0.032667 = 0.32667 kg (326.67 g). For exact results with no rounding error, use the fraction 98/3000: multiply the assay ton value by 98, then divide by 3000. This fractional method is preferred when chaining multiple unit conversions in analytical laboratory or metallurgical reporting workflows.

In what industries and countries is the UK assay ton still in active use?

The UK assay ton remains active in gold and silver mining across the United Kingdom, Australia, Canada, South Africa, and other former British Commonwealth nations where long-ton ore grade reporting persists in legacy contracts, regulatory filings, and historical mine records. Fire assay laboratories, bullion trading houses, and mineral resource consulting firms encounter this unit regularly when reconciling modern metric data with pre-1970s assay archives or when serving clients operating under imperial-unit contractual obligations.