Calcady™
Home / Unit / Weight Conversion Calculator

Weight Conversion Calculator

Convert weight between pounds, kilograms, ounces, grams, tons, stones, and other weight units instantly.

Mass Converter

68.0388

Converted Value

68.0388
Kilograms
Email LinkText/SMSWhatsApp

What is Mass vs Weight: Kilograms, Pounds & Force Units?

The critical physics distinction between mass (a property of matter) and weight (a force due to gravity) — and why 'pound' means different things in different engineering contexts.

Mathematical Foundation

Weight Force from Mass
W=m×gW = m \times g
mm= Mass in kilograms (kg) — the amount of matter, constant everywhere in the universe
gg= Gravitational acceleration = 9.80665 m/s² (standard gravity at Earth's surface)
WW= Weight force in Newtons (N) — varies with gravity (W on Moon = m × 1.62 m/s²)

Laws & Principles

  • Mass vs. Weight: Mass (kg) is the measure of matter — your 70 kg body has 70 kg of mass everywhere, including on the Moon. Weight is the gravitational force acting on that mass: on Earth, 70 kg × 9.81 m/s² = 686.7 N. On the Moon (g=1.62 m/s²), your weight drops to 113.4 N — but your mass remains 70 kg. A 'scale' in everyday use measures weight force, then divides by g to display kg.
  • The Pound Confusion: In everyday American usage, 'pound' means pound-mass (lbm) — 1 lb = 0.453592 kg exactly by international definition. However, aerospace and mechanical engineers also use 'pound-force' (lbf), where 1 lbf = the force that g exerts on 1 lbm = 4.44822 N. A 'ton' adds another layer: metric ton = 1,000 kg, US short ton = 2,000 lbs = 907.185 kg, UK long ton = 2,240 lbs = 1,016.05 kg.

Step-by-Step Example Walkthrough

" Converting 150 pounds to kilograms and Newtons of weight force. "

  1. Mass: 150 lb × 0.453592 kg/lb = 68.039 kg.
  2. Weight force on Earth: 68.039 kg × 9.80665 m/s² = 667.2 N.
  3. Weight force on Moon: 68.039 kg × 1.62 m/s² = 110.2 N.
Final Result: 150 lb = 68.04 kg = 667.2 N (Earth) = 110.2 N (Moon)

Quick Answer: Common Weight Conversions

1 pound = 0.4536 kg. 1 kg = 2.2046 lbs. 1 ounce = 28.3495 grams. 1 stone = 14 lbs = 6.35 kg. 1 US ton = 2,000 lbs (short ton). 1 metric tonne = 2,204.6 lbs = 1,000 kg.

Weight Conversion Reference

FromToMultiply By
Pounds (lbs)Kilograms0.45359
KilogramsPounds2.20462
Ounces (oz)Grams28.3495
StonePounds14
Short Ton (US)Metric Tonne0.90718
Troy OunceGrams31.1035

Troy ounces (31.1g) are used for precious metals. Avoirdupois ounces (28.35g) are used for everything else. Gold priced at "$2,000 per ounce" means troy ounces.

Frequently Asked Questions

What is the difference between mass and weight?

Mass is the amount of matter (measured in kilograms). Weight is the gravitational force on that mass (measured in newtons). A 70 kg person has a mass of 70 kg everywhere, but weighs 686 N on Earth and 114 N on the Moon. In everyday use, "weight" and "mass" are used interchangeably because we're always on Earth where gravity is constant.

Why are there three different types of tons?

Short ton (US) = 2,000 lbs. Long ton (Imperial) = 2,240 lbs. Metric tonne = 1,000 kg = 2,204.6 lbs. The short ton is used in US commerce and shipping. The long ton is used in British shipping and naval displacement. The metric tonne is the international standard. When buying bulk materials (gravel, steel, grain), always confirm which "ton" is being quoted — the difference between a short ton and metric tonne is 10%.

What is a troy ounce?

A troy ounce (31.1035g) is heavier than a regular (avoirdupois) ounce (28.3495g). Troy ounces are used exclusively for precious metals — gold, silver, platinum. When gold is quoted at "$2,000 per ounce," it means troy ounces. Confusingly, a troy pound (12 troy oz = 373.2g) is lighter than a regular pound (16 oz = 453.6g). The troy system dates back to the medieval French city of Troyes.

Related Converters