Why is a troy ounce different from a regular ounce?

The troy ounce (31.1035 g) is used for precious metals like gold and silver. The avoirdupois ounce (28.3495 g) is used for everything else. A "kilo of gold" weighs 32.151 troy ounces.

The slug is the imperial unit of mass that gives 1 lbf when accelerated at 1 ft/s². It equals approximately 14.5939 kg.

🔄 Conversion

Mass Converter

A scientific mass converter — supports the everyday units (kg, g, lb, oz) PLUS the carat, troy ounce, slug and atomic mass unit (u) used in physics, chemistry and jewellery.

Last reviewed: January 2026 Formula shown No signup required

Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.

Mass Converter

Scientific Mass — Includes Slug, Carat, Atomic Mass Units

Value to Convert

Enter any number (decimals allowed).

From

📐 Formula & Method

Linear conversion

result = value × (factor_from / factor_to)

All units are stored as a multiplier against an internal base unit. To convert, the input is first scaled to the base, then divided by the target factor.

📋 How to Use

1
Enter the numeric value you want to convert.
2
Pick the source unit in the From dropdown.
3
Pick the target unit in the To dropdown.
4
Click Calculate. You will see the result, a full conversion table to every supported unit, and a list of common conversions.

💡 Key Insights

1 metric carat = exactly 200 mg — the international gemstone standard since 1907.
1 troy ounce = 31.1035 g (used for precious metals); the regular avoirdupois ounce = 28.3495 g.
The slug is the imperial mass unit consistent with force in pounds and acceleration in ft/s² — 1 slug ≈ 14.594 kg.
1 atomic mass unit (u or Da) = 1.6605 × 10⁻²⁷ kg, defined as 1/12 the mass of a ¹²C atom.

🔬 Methodology & Accuracy

Formula: Linear unit conversion with high-precision constants. All math runs client-side in your browser using IEEE-754 doubles.

Data sources: BIPM SI brochure (9th ed.); NIST SP 811 (2008 ed.); ISO 80000-1 quantities and units.

Last reviewed: January 2026 · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.

For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.

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❓ Frequently Asked Questions

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