What Is Kilogram?
A kilogram is a unit we use to measure how much mass something has. It is the main unit of mass in the metric system and in science around the world.
Definition
A kilogram is the base unit of mass in the International System of Units, called SI. When you check your weight on a scale, the number you see is usually in kilograms.
In very simple words, the kilogram tells us how much stuff or matter is inside an object. A school backpack, a bag of rice, or a laptop can all be measured in kilograms.
In modern science, the kilogram is defined using a constant from physics called the Planck constant. This makes the kilogram very exact and the same everywhere in the world.
History / Origin
The idea of the kilogram began in France in the late 1700s, when people wanted a fair and simple system of measurement that everyone could share.
- At first, one kilogram was meant to be the mass of one liter of pure water at a certain temperature.
- Later, around 1889, the kilogram was fixed using a special metal cylinder made of platinum and iridium. This object was kept in a secure place near Paris and became the official reference for the whole world.
- In 2019, the definition changed again. Scientists stopped using the metal cylinder and started using the Planck constant, measured with very precise instruments. This new way does not depend on any object that can change or get damaged.
Thanks to these changes, the kilogram is now based on the laws of physics, which are the same at all times and in all places.
Symbol & Abbreviation
The symbol for kilogram is kg.
- Full name kilogram
- Symbol kg
- Plural kilograms, often written as kg as well
The symbol uses lowercase letters. You should not write it as KG or Kg in formal science work. The correct form is always kg.
Current Use Around the World
The kilogram is used almost everywhere in the world for measuring mass.
- In science Kilograms are used in physics, chemistry, engineering and medicine to measure mass in a standard way.
- In shops Food like fruit, vegetables, flour and meat is often sold by the kilogram or by parts of a kilogram, such as 0.5 kg.
- In health Body mass is usually given in kilograms in medical records and on bathroom scales in most countries.
- In industry Factories and companies use kilograms and metric tons to measure materials and goods.
Some countries, like the United States, still use pounds in daily life, but even there, scientists and many industries use kilograms in their work.
Example Conversions
Here are some simple and useful conversions related to kilograms.
Between kilograms and grams
- 1 kilogram = 1000 grams
- 0.5 kilogram = 500 grams
- 2 kilograms = 2000 grams
To change kilograms to grams, multiply by 1000.
To change grams to kilograms, divide by 1000.
Between kilograms and milligrams
- 1 kilogram = 1,000,000 milligrams
- 0.001 kilogram = 1,000 milligrams
Between kilograms and metric tons
- 1 metric ton = 1000 kilograms
- 0.5 metric ton = 500 kilograms
Between kilograms and pounds
Pounds are used in the imperial system, mainly in the United States and a few other places.
- 1 kilogram is about 2.2046 pounds
- 1 pound is about 0.4536 kilograms
Quick rule for mental math. To change kilograms to pounds, multiply by about 2.2. To change pounds to kilograms, divide by about 2.2.
Everyday examples
- A small textbook might have a mass of about 1 kilogram.
- A big bag of rice could be 5 kilograms.
- A new baby might have a mass of about 3 to 4 kilograms.
Related Units
There are many other units connected to the kilogram.
- Gram (g) One gram is one thousandth of a kilogram. 1000 g = 1 kg.
- Milligram (mg) One milligram is one thousandth of a gram. 1,000,000 mg = 1 kg.
- Microgram (µg) One microgram is one millionth of a gram. Used for very small masses like medicine doses.
- Metric ton or tonne (t) One metric ton is 1000 kilograms. Used for heavy items like trucks or cargo.
- Pound (lb) An imperial unit. 1 lb is about 0.4536 kg.
- Ounce (oz) An imperial unit. 1 oz is about 28.35 g, which is 0.02835 kg.
- Stone (st) Used in a few countries for body mass. 1 stone is 14 lb, which is about 6.35 kg.
FAQs
Is kilogram a unit of mass or weight
The kilogram is a unit of mass. Mass is how much matter is in an object. Weight is the force of gravity on that mass. On the Moon your mass in kilograms would be the same but your weight would be less because gravity is weaker there.
Why is kilogram the base unit instead of gram
At the start of the metric system, scientists chose the kilogram as the main unit because it was a convenient size for everyday objects. Most common items like food and tools are easier to measure in kilograms than in grams, so the kilogram became the official base unit of mass.
How do I quickly convert body weight from kilograms to pounds
You can use this simple trick. Multiply your mass in kilograms by 2.2 to get pounds. For example, 60 kg x 2.2 is about 132 lb. To go back to kilograms, divide the pounds by 2.2.
Can I write kilogram as kilo
In casual speech, many people say kilo instead of kilogram, for example a kilo of apples. But in science and formal writing, you should use the full word kilogram or the symbol kg, not kilo.
Where do we mostly use kilograms in daily life
We use kilograms to measure body mass, food in shops, luggage at airports, and many household items. Doctors, teachers, and engineers also use kilograms when they record masses in their work.