What Is Mass?
Mass is a fundamental property of matter that measures the amount of substance in an object. Unlike weight, which depends on gravity, mass remains constant regardless of where you are in the universe. A 5 kg dumbbell has the same mass on Earth, on the Moon, and in deep space.
Mass is measured in a wide variety of units depending on the context, from micrograms for pharmaceutical dosing to metric tons for industrial cargo. This calculator converts between all major mass units instantly.
What This Calculator Does
Enter a mass value and select a unit. The calculator instantly displays the equivalent mass in all supported units simultaneously, including:
- Kilogram (kg), gram (g), milligram (mg), microgram (μg)
- Metric ton (t)
- Pound (lb), ounce (oz), stone (st)
- Slug (used in imperial physics)
How the Calculation Works
All conversions use kilograms as the base unit. Each unit has a fixed conversion factor relative to one kilogram. To convert from any unit to any other, the calculator first converts the input to kilograms, then converts from kilograms to the target unit.
Value in kg = input × (unit's kg factor)
Result = Value in kg / (target unit's kg factor)
For example, to convert 5 pounds to kilograms: 5 × 0.453592 = 2.268 kg. To convert 2.268 kg to grams: 2.268 / 0.001 = 2,268 g.
How to Use the Calculator
- Enter the mass value in the input field
- Select the unit you are converting from
- All equivalent values appear instantly in the results panel
- The input unit is highlighted for easy reference
Example Calculations
Example 1: 1 kg in common units
1 kilogram = 1,000 grams = 1,000,000 milligrams = 2.205 pounds = 35.27 ounces = 0.157 stone.
Example 2: 150 pounds to kilograms
150 lb × 0.453592 = 68.04 kg. A person weighing 150 pounds has a mass of approximately 68 kilograms.
Real-World Scenarios
Pharmacy and Medicine
Drug dosages are often prescribed in milligrams (mg) per kilogram of body weight. A patient needs to convert their body mass to kg to calculate the correct dose from a mg/kg prescription.
Shipping and Logistics
International shipping often requires converting between metric tons, kilograms, and pounds because different carriers and countries use different units for weight limits and tariff calculations.
Cooking and Nutrition
Recipes from different countries use grams or ounces. A nutritional label might show serving size in grams while a recipe calls for ounces. Instant conversion eliminates guesswork.
Why This Calculation Matters
Mass conversions appear in science, medicine, shipping, fitness, cooking, and engineering. Using the wrong unit can mean the difference between a correct medication dose and a dangerous one, or between a package being accepted or rejected at customs. Accurate conversion is a basic but critical skill.
Common Mistakes to Avoid
- Confusing mass and weight: Mass is measured in kg or lbs as a quantity of matter. Weight is a force measured in Newtons. In everyday language they are used interchangeably, but in physics they are different
- UK vs US units: The pound (lb) is the same in both systems, but the UK stone (14 lbs) is not used in the US. The UK hundredweight is 112 lbs while the US hundredweight is 100 lbs
- Metric prefix confusion: Milli means 1/1000, micro means 1/1,000,000. A milligram is 1,000 times heavier than a microgram, not 1,000,000 times