Weight Converter

Metric units (mcg, mg, g, kg, tonne) scale by powers of 10 around the kilogram, the SI base unit of mass.

Imperial / US units (ounce, pound, stone, ton) use legacy ratios:

• 16 oz = 1 lb
• 14 lb = 1 stone
• 2,000 lb = 1 US (short) ton
• 2,240 lb = 1 UK (long) ton

Cross-system conversions use fixed factors:

• 1 lb = 453.59237 g
• 1 oz = 28.349523125 g
• 1 metric tonne = 1,000 kg ≈ 2,204.62 lb

Our weight converter handles both systems bidirectionally with no rounding surprises.

Beyond everyday units, this tool supports:

• troy ounces (31.1034768 g) for precious metals like gold and silver
• carats (0.2 g) for gemstones and diamonds
• grains (64.79891 mg) for bullets, arrows, and pharmaceuticals
• micrograms (10⁻⁶ g) for medicine dosing and lab work

— all converted through grams as the common base.

Whether you are pricing gold, measuring a diamond, estimating shipping weight, or converting a cooking recipe, the weight converter gives you an instant, accurate answer.

To convert kilograms to pounds, multiply the kilogram value by 2.20462; to go from pounds to kilograms, divide by 2.20462 (or multiply by 0.45359237).

These factors come from the exact definition of the international avoirdupois pound as 0.45359237 kilograms, fixed by international agreement and published by NIST in Special Publication 811.

For example, 70 kg × 2.20462 = 154.32 lb, and 150 lb ÷ 2.20462 = 68.04 kg.

Because the kilogram is the SI base unit of mass (defined by BIPM through the Planck constant since 2019), every other weight unit in this converter is anchored to it, ensuring consistent, repeatable results.

One avoirdupois ounce equals exactly 28.349523125 grams, and one troy ounce equals exactly 31.1034768 grams.

The avoirdupois ounce is the everyday ounce used for food, mail, and general goods, defined as 1/16 of the international pound (453.59237 g), a value fixed by NIST and international standards bodies.

To convert ounces to grams, multiply by 28.349523125; to convert grams to ounces, divide by the same factor.

For precious metals, use the troy ounce instead, since it is roughly 10% heavier. Confusing the two is a common source of pricing errors, so always confirm which ounce a quote refers to before converting.

One stone equals exactly 14 pounds, which is approximately 6.35029 kilograms (14 × 0.45359237 kg).

To convert stone to pounds, multiply by 14; to convert stone to kilograms, multiply by 6.35029.

Body weight in the United Kingdom and Ireland is commonly expressed in stone and pounds, such as "11 stone 4" meaning 11 stone plus 4 pounds (158 lb, about 71.7 kg). To convert back, divide the pound value by 14 to get whole stone, with the remainder as leftover pounds.

The stone is a traditional imperial unit still recognized in everyday British usage, though not part of the SI defined by BIPM.

Gold, silver, platinum, and other precious metals are weighed in troy ounces, not the ordinary avoirdupois ounces used for groceries.

One troy ounce equals exactly 31.1034768 grams, while one avoirdupois ounce equals 28.349523125 grams, making the troy ounce about 9.7% heavier. So when gold is quoted at a price "per ounce," it means per troy ounce.

There are 12 troy ounces in a troy pound (373.24 g), not 16, which is another difference from the avoirdupois system.

NIST documents both systems; mixing them up can distort a bullion valuation by nearly ten percent, so always specify troy for metals.

One metric carat equals exactly 0.2 grams, or 200 milligrams, by international definition.

To convert carats to grams, multiply by 0.2; to convert grams to carats, divide by 0.2 (multiply by 5). A 1-carat diamond therefore weighs 0.2 g, and a 5-carat stone weighs exactly 1 gram.

The metric carat used for gemstones should never be confused with karat (spelled with a K), which measures gold purity on a 24-part scale, not weight.

The carat is a legally recognized unit of mass for precious stones in most jurisdictions and traces back to standardization efforts aligned with the metric system maintained by BIPM.

Three different "tons" exist, and confusing them causes major freight and shipping errors:

• A US (short) ton equals 2,000 pounds, roughly 907.185 kilograms.
• A UK (long) ton equals 2,240 pounds, roughly 1,016.047 kilograms.
• A metric ton, or tonne, equals exactly 1,000 kilograms, roughly 2,204.62 pounds — the version recognized within the SI framework described by BIPM.

To convert a metric ton to US tons, multiply by about 1.10231; to UK tons, multiply by about 0.98421.

Because a metric ton sits between the two imperial tons, always confirm which system a quote or spec sheet uses before converting shipping or material weights.

A weight converter is essential across many everyday and professional tasks:

• International shoppers and shippers convert kilograms to pounds to compare parcel rates and avoid overweight fees.
• Cooks translate metric recipe grams into ounces and pounds, and vice versa, though ingredient density still matters for volume conversions.
• Athletes and dieters switch between kg, lb, and stone to track body weight across regions.
• Jewelers price gemstones in carats and precious metals in troy ounces.
• Pharmacists and clinicians dose medication in milligrams and micrograms per kilogram of body weight, where accuracy is safety-critical.
• Reloaders measure bullets and powder in grains.

Anchoring all of these to grams keeps every conversion consistent and reliable.

The metric mass units scale cleanly by powers of ten, which makes conversions simple. One gram equals 1,000 milligrams (mg) and 1,000,000 micrograms (mcg or µg).

So one milligram equals 1,000 micrograms, and one microgram equals 10⁻⁶ grams. To convert grams to milligrams, multiply by 1,000; to convert milligrams to micrograms, multiply by 1,000 again.

These SI prefixes — milli- (10⁻³) and micro- (10⁻⁶) — are defined by BIPM and NIST and apply uniformly across all metric quantities.

Micrograms are common in vitamin and drug dosing, milligrams in nutrition labels and pharmaceuticals, and grams in cooking and general measurement.

Common weight conversion mistakes to avoid:

• The most frequent weight conversion error is confusing troy ounces with avoirdupois ounces, which distorts precious-metal values by nearly 10%.
• Another is assuming all "tons" are equal — US short tons, UK long tons, and metric tonnes differ by hundreds of kilograms.
• People also mix up carat (gemstone mass, 0.2 g) with karat (gold purity), and stone (14 lb) with pounds.
• A subtler error is treating weight and volume conversions as identical: converting grams to cups depends on ingredient density, so it is not a fixed factor.
• Finally, over-rounding early — for example using 2.2 instead of 2.20462 for kg-to-lb — compounds into noticeable errors on large values.

Anchoring to exact factors avoids all of these.