⚖️ Mass & Weight Conversion

Convert between mass and weight units with precision. Supports metric units (kilogram, gram, milligram, metric ton), imperial units (pound, ounce, stone, US ton), and scientific units (atomic mass unit, electron volt). Whether you are tracking fitness goals, calculating shipping weights, or doing chemistry homework, the mass converter handles it all with up to 12 decimal places of precision.

Mass and weight conversion calculates equivalent mass across metric, avoirdupois imperial, and troy systems using fixed international standards. Standardized by the BIPM 2019 SI Redefinition and NIST SP 811, 1 kilogram (kg) is the SI base unit (defined by the Planck constant h), 1 avoirdupois pound (lb) equals exactly 0.45359237 kg, and 1 ounce (oz) equals 28.3495 grams.

Metrological Standards & Base Equation

1 kilogram = 2.20462 pounds. 1 pound = 453.592 grams. 1 stone = 6.35029 kilograms.

All mass conversion factors comply with the 2019 BIPM SI Redefinition of the kilogram via the Planck constant, NIST Special Publication 811, and the 1959 International Yard and Pound Agreement (codifying 1 lb = 0.45359237 kg exact). Precious metal conversions strictly adhere to the Troy ounce standard (1 oz t = 31.1034768 grams).

Primary References: NIST SP 811 (2008 Edition) · BIPM SI Brochure (2019) · Standards Directory

Supported Mass Units (13 Total)

Mass Unit Definitions and Scaling Factors
Unit Symbol Unit Name System Equivalent in Kilogram
µg Microgram Metric 1 µg = 1.000000e-9 kg
mg Milligram Metric 1 mg = 0.000001 kg
g Gram Metric 1 g = 0.001 kg
kg Kilogram Metric SI Base Unit (1 kg)
t Metric Ton Metric 1 t = 1000 kg
oz Ounce Imperial 1 oz = 0.0283495 kg
lb Pound Imperial 1 lb = 0.453592 kg
st Stone Imperial 1 st = 6.35029 kg
sh tn Short Ton Imperial 1 sh tn = 907.185 kg
lg tn Long Ton Imperial 1 lg tn = 1016.05 kg
ct Carat Other 1 ct = 0.0002 kg
gr Grain Imperial 1 gr = 0.0000648 kg
amu Atomic Mass Unit Scientific 1 amu = 1.660539e-27 kg

Popular Mass Conversions

Kilogram to Pounds

kg → lb — fitness & body weight tracking

Pounds to Kilogram

lb → kg — international shipping & travel

Ounces to Grams

oz → g — cooking & baking recipes

Stone to Kilogram

st → kg — UK body weight to metric

Metric Ton to US Ton

t → ton — industrial & freight

Conversion Guides & Step-by-Step Formulas

Step-by-step formula derivation, worked examples, and quick lookup tables.
Step-by-step formula derivation, worked examples, and quick lookup tables.

Common Use Cases

  • Fitness & body weight (kg↔lb)
  • Cooking & recipes (oz↔g, lb↔g)
  • Shipping & logistics (kg↔lb, t↔ton)
  • Science & chemistry (amu, g)
  • Jewelry & precious metals (oz↔g)

Frequently Asked Questions

How many pounds in a kilogram?

One kilogram equals 2.20462 pounds. Multiply kg by 2.20462 to get pounds.

How do I convert ounces to grams?

Multiply ounces by 28.3495 to get grams. For example, 8 oz × 28.3495 = 226.8 grams.