Weight Calculator

Formula

Output = Input × (From Unit Factor ÷ To Unit Factor)

Convert through kilograms as base unit. Multiply input by the 'from' conversion factor, then divide by the 'to' conversion factor.

Worked Examples

Example 1: Body Weight Conversion

Problem:Convert 175 pounds to kilograms and stones.

Solution:Pounds to kg: 175 lb ÷ 2.205 = 79.4 kg Pounds to stones: 175 ÷ 14 = 12 stone 7 lbs (175 = 12×14 + 7)

Result:79.4 kg or 12st 7lb

Example 2: Shipping Weight

Problem:A package weighs 2.5 kg. What is this in pounds and ounces?

Solution:Kg to pounds: 2.5 × 2.205 = 5.51 lb To pounds and ounces: 5 lb + (0.51 × 16) oz = 5 lb 8.2 oz

Result:5 lb 8.2 oz

Example 3: Recipe Conversion

Problem:A recipe calls for 8 oz of flour. How many grams is that?

Solution:Ounces to grams: 8 oz × 28.35 = 226.8 g For baking, round to: 225-230 grams

Result:227 grams

Frequently Asked Questions

How do I convert pounds to kilograms?

Divide pounds by 2.205 or multiply by 0.4536 to get kilograms. For example, 150 lbs ÷ 2.205 = 68.04 kg. For quick estimation, divide pounds by 2.2.

What's the difference between mass and weight?

Mass (kg) is the amount of matter, constant everywhere. Weight (Newtons) is gravitational force on mass, varying by location. On Earth, we often use 'weight' to mean mass in everyday language.

How many ounces are in a pound?

There are 16 ounces in 1 pound. To convert pounds to ounces, multiply by 16. To convert ounces to pounds, divide by 16.

What is a stone?

A stone is a British unit equal to 14 pounds (6.35 kg). It's commonly used in the UK and Ireland for body weight. 150 lbs = 10 stone 10 lbs.

How do I convert grams to ounces?

Divide grams by 28.35 to get ounces. 100 grams = 3.53 oz. For cooking, 1 oz ≈ 28g is often precise enough.

What's the difference between metric and short tons?

Metric ton = 1000 kg = 2204.6 lb. Short ton (US) = 2000 lb = 907.2 kg. Long ton (UK) = 2240 lb = 1016 kg. Always clarify which 'ton' is meant.

How do I convert my body weight?

For kg to lb: multiply by 2.205. For lb to kg: divide by 2.205. For stones: divide pounds by 14. A 70kg person weighs 154 lb or 11 stone.

What's the smallest common weight unit?

Milligrams (mg) for everyday use, micrograms (μg) for medicine/science. 1 gram = 1000 mg = 1,000,000 μg. A grain of salt weighs about 60 mg.

How accurate should weight conversions be?

For cooking: 1 decimal place. For shipping: whole numbers usually. For science/medicine: 3+ decimal places. For jewelry: 2-3 decimals. Context determines needed precision.

Background & Theory

Weight and mass are often used interchangeably in everyday language, but technically they're different. Mass measures the amount of matter; weight is the force of gravity on that mass.

Common Weight Units:

Metric:

Kilogram (kg) - SI base unit
Gram (g) = 0.001 kg
Milligram (mg) = 0.000001 kg
Metric ton (t) = 1000 kg

Imperial/US:

Pound (lb) = 0.4536 kg
Ounce (oz) = 1/16 lb = 28.35 g
Stone (st) = 14 lb (UK only)
Short ton = 2000 lb (US)
Long ton = 2240 lb (UK)

Key Conversions:

1 kg = 2.205 lb
1 lb = 16 oz
1 oz = 28.35 g
1 stone = 14 lb
1 metric ton = 1000 kg = 2205 lb

Precision:
Scientific measurements use SI units (kg, g) with high precision. Everyday weights typically use practical units with 1-2 decimal places.

Weight vs Mass:
On Earth, weight (N) = mass (kg) × 9.81 m/s²
On Moon, weight is 1/6 of Earth weight
Mass remains constant everywhere

History

Weight measurement is among humanity's oldest technologies. Ancient Egyptians used balance scales with stone weights around 5000 BCE. The first standardized weights emerged for trade - accurate measurement was essential for fair commerce. The pound has Roman origins: "libra pondo" (a pound by weight), giving us both the name "pound" and the abbreviation "lb." The Roman pound was about 327 grams. The metric system's kilogram was defined in 1795 as the mass of one liter of water at 4°C. A physical kilogram prototype was created in 1889, kept in Paris and used as the world standard until 2019. The 2019 redefinition tied the kilogram to the Planck constant, a fundamental physical constant, ensuring the standard could never change or be damaged. This was the last SI base unit to be defined by a physical object. Different weight systems persist globally. The US uses pounds and ounces; the UK uses stones for body weight but metric elsewhere. Science universally uses kilograms and grams.