Calculated using standard mathematical and industry formulas.
Weight and mass conversions translate values between metric SI units and avoirdupois imperial systems according to exact international treaty standards. One pound equals precisely 16 ounces or 0.45359237 kilograms, one ounce equals 28.3495 grams, and one stone equals 14 pounds. This tool provides instant, high-precision conversions across all commercial and scientific units.
How to use this calculator?
Enter the weight value you want to convert.
Select the starting unit of weight ('From').
Select the target unit of weight ('To').
Read your converted value instantly, along with the exact conversion factor and equivalent metric/imperial values.
Formula & calculation method
SI Base Conversion Factor Method
Value in Target Unit = (Value in Source Unit × Factor to Kilograms) ÷ Factor Target Unit to Kilograms; 1 lb = 16 oz = 0.45359237 kg; 1 oz = 28.349523 g; 1 kg = 1,000 g = 2.20462262 lb; 1 st = 14 lb = 6.350293 kg
Factors: 1 kg = 1, 1 g = 0.001, 1 mg = 1e-6, 1 lb = 0.45359237, 1 oz = 0.028349523125, 1 st = 6.35029318.
Step-by-step calculation example
Convert 100 kg to lb: 100 × 1.0 ÷ 0.45359237 ≈ 220.4623 lb.
Key insights to remember
The kilogram (kg) is the base unit of mass in the International System of Units (SI).
1 pound (lb) is legally defined as exactly 0.45359237 kilograms in international trade.
1 stone (st) is an imperial unit equal to exactly 14 pounds (approx. 6.35 kg), commonly used for body weight in the UK.
1 ounce (oz) is equal to 1/16th of a pound (approx. 28.35 grams).
1 kilogram equals 1,000 grams or 1,000,000 milligrams.
How to interpret your results?
Avoirdupois Ounce vs. Troy Ounce
Standard kitchen, shipping, and body weights use the avoirdupois ounce (1 oz = 28.3495 g; 16 oz per lb). In contrast, precious metals (gold, silver) use the troy ounce, which is heavier at 31.1035 grams (12 troy oz per troy lb).
Everyday Kitchen & Metric Anchors
Useful kitchen heuristics: 1 stick of US butter is 4 oz (1/4 lb or 113.4 g). 1 kilogram is roughly 2.2 pounds, and 100 grams is about 3.5 ounces.
Expert advice & guidance
💡 Precision trade tip: When purchasing precious metals, jewelry, or pharmaceuticals, always confirm whether pricing is quoted in troy ounces (31.10 g) or standard avoirdupois ounces (28.35 g) to prevent costly 10% valuation discrepancies.
Frequently asked questions
How many ounces are in a pound and how many oz in a pound?
There are exactly 16 ounces (oz) in one avoirdupois pound (lb). To convert pounds to ounces, multiply the number of pounds by 16 (e.g., 5 lbs × 16 = 80 oz). Conversely, to convert ounces to pounds, divide the ounces by 16 (e.g., 32 oz ÷ 16 = 2 lbs).
How many grams are in an ounce and how many grams in an oz?
There are exactly 28.349523125 grams in one standard avoirdupois ounce (commonly rounded to 28.35 grams in cooking and nutrition). In precious metals, a troy ounce equals 31.1035 grams. For quick kitchen math, 1 ounce is approximately 28 grams.
How many milligrams (mg) are in a gram?
There are exactly 1,000 milligrams (mg) in one gram (g). To convert grams to milligrams, multiply by 1,000 (e.g., 0.5 g = 500 mg). To convert milligrams to grams, divide by 1,000 (e.g., 250 mg = 0.25 g). The metric prefix 'milli' means one-thousandth (1/1,000).
How many grams are in a kilogram (kg)?
There are exactly 1,000 grams in one kilogram (kg). The prefix 'kilo' represents 1,000 in the International System of Units (SI). Therefore, 2.5 kg equals 2,500 grams, and 750 grams equals 0.75 kilograms.
How many pounds are in a stone and how many lbs in st?
There are exactly 14 pounds (lbs) in one stone (st), which equals approximately 6.35029 kilograms. Stones are widely used in the United Kingdom and Ireland to report human body weight. For example, 10 stone equals 140 lbs (63.5 kg), and 12 stone equals 168 lbs (76.2 kg).
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