Weight Converter

Weight Unit Conversion — Complete Guide

Weight (more precisely, mass) is measured in dozens of different units across the world — from the metric kilogram used in most countries to the imperial pound dominant in the US, and even traditional units like the Arabic mithqal still used in some jewelry markets. The Toolsiro Weight Converter supports 13 units spanning metric, imperial, and traditional scales, converting between all of them instantly as you type.

Metric Weight Units

• Metric Ton (t): 1,000 kg. Used for large-scale measurements — cargo capacity, vehicle weight limits, industrial production output, and grain harvests. A small car weighs about 1.2–1.5 metric tons.
• Kilogram (kg): The SI base unit of mass. Defined since 2019 by the Planck constant. The global standard for body weight, food packaging, luggage allowances, and most everyday measurements.
• Gram (g): 1/1,000 kg. The standard unit for food nutrition labels, cooking recipes, postal rates for letters, and small package weights. A standard paperclip weighs about 1 gram.
• Milligram (mg): 1/1,000 g. Used in pharmacology for medication dosages, chemistry, and nutritional supplements. Vitamins and minerals in food are typically listed in milligrams.
• Microgram (μg): 1/1,000 mg. Used for trace elements, environmental pollutant measurements, and highly potent medications.

Imperial and US Customary Units

• Pound (lb): 0.453592 kg. The primary unit of body weight in the US and to some extent the UK. Also used for food weights in American recipes, postal rates, and fitness contexts. A pound is 16 ounces.
• Ounce (oz): 28.35 g. Used for food portions in the US (a standard burger patty is 4 oz), precious metals (gold and silver prices are quoted per troy ounce, which is slightly heavier at 31.1 g), and drink sizes.
• Stone (st): 6.35 kg (14 pounds). Predominantly used in the UK and Ireland for human body weight. A person weighing 75 kg weighs approximately 11 stone 11 pounds.
• Long Ton (LT): 1,016.05 kg (2,240 lb). Used in the UK for large-scale industrial measurements and historic shipping.
• Short Ton (ST): 907.185 kg (2,000 lb). Used in the US for truck payload capacity, coal production, and industrial output.

Traditional and Specialist Units

• Carat (ct): 0.2 g. The standard unit for gemstone weight worldwide. A 1-carat diamond weighs exactly 0.2 grams. Note: carat for gold purity is a different unit entirely — it measures fineness, not weight.
• Grain (gr): 64.8 mg. One of the oldest weight units, originally based on the weight of a grain of barley. Still used for ammunition bullet weights and archery arrow weights.
• Mithqal (مثقال): Approximately 4.608 g. A traditional Arabic and Islamic unit of weight historically used across the Arab world and Persia. Still referenced in some Islamic jurisprudence texts for zakat calculations (nisab threshold) and in traditional jewelry markets in the Gulf region.

Weight vs Mass — The Technical Difference

In everyday language, "weight" and "mass" are used interchangeably. Scientifically, they are different: mass is the amount of matter in an object (measured in kg) and is constant everywhere in the universe. Weight is the force exerted on that mass by gravity (measured in newtons) and varies depending on gravitational field strength. On the Moon, your mass is the same as on Earth, but your weight is about 1/6 as much. For all practical everyday purposes — including this converter — the terms are equivalent.

Quick Reference Conversions

• 1 kg = 2.205 lb = 35.27 oz
• 1 lb = 0.4536 kg = 16 oz
• 1 stone = 6.35 kg = 14 lb
• Average adult: ~70 kg = 154 lb = 11 stone
• Luggage allowance 23 kg = 50.7 lb
• Gold price per troy ounce: 1 troy oz = 31.1 g

Related Unit Converters

For length conversions, use the Length Converter. For temperature, use the Temperature Converter. For body weight health assessment, try the BMI Calculator.