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Convert Pounds to Kilograms and Kilograms to Pounds | lbs to kg and kg to lbs Conversion

Pounds and kilograms are units of mass, and understanding the relationship between these units is fundamental for countless applications ranging from scientific research to everyday activities.

This article aims to demystify the process of converting pounds to kilograms and vice versa, providing readers with the knowledge and tools needed to perform these conversions accurately and efficiently - conversion calculators and conversion tables.

Published: February 1, 2024.

lbs to kg and kg to lbs Conversion Calculators

To convert mass expressed in pounds to kilograms and kilograms to pounds, feel free to use the following calculator:

Pounds (lbs) to Kilograms (kg)

Pounds (lbs):

Kilograms (kg):


Kilograms (kg) to Pounds (lbs)

Kilograms (kg):

Pounds (lbs):

How To Convert Pounds to Kilograms and Kilograms to Pounds

The relationship between pounds and kilograms is as follows:

1 lbs = 0.45359237 kg → 1 kg = 1/0.45359237 lbs = ~2.2046226 lbs

Note: One international avoirdupois pound (lbs) is legally defined as being exactly 0.45359237 kilograms (kg).

Pounds to Kilograms and Kilograms to Pounds Conversion Tables

The following tables contain the most common values given in pounds and kilograms, converted into kilograms and pounds:

Kilograms (kg)
Pounds (lbs)
0.1 0.2204
0.5 1.1023
1.0 2.2046
2.0 4.4092
3.0  6.6138
4.0  8.8184
5.0  11.023
6.0  13.227
7.0  15.432
8.0 17.636
9.0  19.841
10.0  22.046
25.0  55.115
50.0  110.23
100.0  220.46
Pounds (lbs)
Kilograms (kg)
0.1 0.0453
0.5 0.2267
1.0 0.4535
2.0  0.9071
3.0  1.3607
4.0  1.8143
5.0  2.2679
6.0  2.7215
7.0  3.1751
8.0  3.6287
9.0  4.0823
10.0  4.5359
25.0  11.339
50.0  22.679
100.0  45.359

If You wish to convert values that are not in the table, please use the conversion calculators.

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Brief History of Kilogram

The story of a kilogram as a unit of mass is not only about measuring weight but also about humanity's quest for precision, standardization, and understanding of the physical world.


The kilogram's history can be traced back to the French Revolution, a period marked by a desire for reform and standardization. In 1795, France officially adopted the metric system, introducing the kilogram as a base unit of mass.

Originally defined as the mass of one liter of water at the freezing point, the kilogram aimed to provide a more rational and universal system of measurement.

The Kilogram Prototype

In 1799, to establish a more precise standard, the kilogram was represented by a platinum cylinder, known as the "Kilogramme des Archives," stored in Paris. This physical artifact served as the benchmark for all mass measurements worldwide.

However, recognizing the need for a more durable and stable standard, the First General Conference on Weights and Measures (CGPM) in 1889 introduced a new prototype.

The kilogram was redefined as the mass of a platinum-iridium alloy cylinder, known as the International Prototype of the Kilogram (IPK), stored at the International Bureau of Weights and Measures (BIPM) in Sèvres, France. This prototype provided the basis for the kilogram for nearly 130 years.

Towards a Constant Definition

Despite the precision of the IPK, scientists recognized that relying on a physical object could lead to inconsistencies over time.

To address this, the 26th CGPM in November 2018 made a historic decision to redefine the kilogram based on a fundamental constant of nature rather than a physical artifact.

This led to the kilogram being defined in terms of the Planck constant (h), effective from May 20, 2019. This redefinition is part of a broader effort to define all SI (International System of Units) base units in terms of universal constants, ensuring greater precision and stability in measurements.

Importance and Usage

The kilogram is crucial in various fields, from science and engineering to commerce and daily life.

It serves as a fundamental unit for mass measurements in the International System of Units (SI), influencing scientific research, industrial production, and even grocery shopping. The kilogram's accurate measurement is vital for precision in experiments, manufacturing processes, and ensuring fair trade practices.

Global Impact

The evolution of the kilogram reflects the global community's commitment to a unified system of measurement.

By basing the kilogram on the Planck constant, scientists have ensured that it can be replicated accurately anywhere in the world, fostering international collaboration and consistency in measurements across different domains.

Brief History of Pound

The pound, a unit of weight commonly used in the United States, United Kingdom, and other countries, has a rich and varied history that spans several millennia.

Unlike the kilogram, which has a more unified history, the story of the pound is characterized by its diversity and the multitude of "pounds" that have existed throughout history.


The origin of the pound dates back to the Roman libra, from which the abbreviation lb is derived. The libra was approximately 328.9 grams and was divided into 12 unciae, or ounces. This ancient root reflects the pound's long-standing significance in trade and measurement systems.

Various Pounds and Their Values

Over the centuries, the pound has been defined and redefined in numerous contexts, leading to a variety of "pounds" with different values:

  • Tower Pound: Used in England until the 16th century, it was equivalent to 350 grams.
  • Troy Pound: Traditionally used for precious metals, one troy pound equals 373.24 grams.
  • Avoirdupois Pound: The most commonly used pound today, especially in the United States, is the avoirdupois pound, which is legally defined as exactly 0.45359237 kilograms.

These variations reflect the adaptations of the pound to meet the needs of different trades and regions.

Importance and Standardization

The importance of the pound lies in its widespread use in commerce, science, and daily life. It serves as a critical unit for weight in countries still using the imperial system or the United States customary system.

Its value and definition have been standardized in various ways throughout history, most notably through the International Yard and Pound Agreement in 1959, which defined the pound in terms of the kilogram.


Today, the pound is widely used in the United States for measuring body weight, produce, and packaged goods, among other items. In countries that have adopted the metric system, the pound is still used informally in colloquial speech or in specific contexts like body weight.

Challenges and Evolution

The diversity of pounds and the transition to the metric system in many parts of the world have presented challenges in standardization and conversion. The multiplicity of standards historically led to confusion in trade and science, prompting efforts to adopt a more universal system of measurement.

Despite these challenges, the pound remains an integral part of measurement systems in several countries, illustrating the complexity and evolution of human measurement systems.