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Algebraic Steps / Dimensional Analysis Formula

* 
0.453592 kg 1 
= 
kg 
Conversion to common lengths
Grains  

Drams  
Ounces  
Pounds  
Stones  
Grams  
Kilograms  
Tons 
< == >
Algebraic Steps / Dimensional Analysis Formula

* 
1 lb 0.453592 
= 
lb 
Conversion to common lengths
Grains  

Drams  
Ounces  
Pounds  
Stones  
Grams  
Kilograms  
Tons 
Pounds and kilograms – the difference
Table of contents
 History of the “pound” as a unit of weight
 Different systems of measurement of the pound
 Relationship between “pounds” and “kilograms”
 Converting from “pounds” of weight to “kilograms”
 Facilitation of conversion calculation
 Practical examples using “pounds” and “kilograms”
 Study of the “pound” and its derived units:
 Examples of comparison with everyday objects
 Problems between conversions
The curiosity of humanity has led it to advance by leaps and bounds compared to other beings in the animal kingdom.
Because of that humankind had many discoveries and scientific advances that have led us to our current technological achievements.
History of the “pound” as a unit of weight
In order to carry out their activities as accurately as possible, humans had to officially declare how to measure the world around them.
A good example was when building a bridge. The ancient Romans had to deduce the approximate weight that a bridge could withstand based on its length and the mass of people, animals and merchandise that would pass through it. To measure the length of large objects, the Romans invented the “Roman foot” which is equivalent to 29.6 centimeters (cm) today.
As its name implies, the “Roman foot” was the approximate length of a common person’s right foot (the left foot was considered bad luck in ancient Rome). For weight, the Romans devised a unit of mass called the “Roman pound” that is currently equivalent to 273 grams (g).
The “Libra avoirdupois” (in English “Pound avoirdupois”) belongs to the socalled “AngloSaxon system” or “imperial system” of measures. It is commonly called simply “pound” or “pounds (plural)” in English. In this text, when we refer to the pound, we will be referring to the “avoirdupois pound”. This system has its origin in the United Kingdom and is a derivative of the measurement systems used by the ancient Romans. As it was adapted by the British colonies as the British Empire expanded around the world, the system was also called the “imperial system”.
This system has the following basic units:
 Inches (in), feet (ft), yards (yd), and miles (mi) as units of length.
 Acres (ac) as a unit of area or surface.
 Ounces and gallons as units of volume for liquids.
 Cubic inches, cubic feet and cubic yards to measure volumes of solids.
 Pounds (lb/lbs) and ounces (oz) as units for measuring the mass of bodies for example.
Different systems of measurement of the pound
However, these measurements proved not always to be completely accurate. After the fall of the Roman Empire, many regions of Europe adapted their own measurement of mass (pound) which would make it even more difficult to have a unit of mass with which to accurately weigh any object.
We can briefly review several historical “pounds” that have been defined over the years and are currently obsolete:
 The AngloSaxon pharmaceutic pound (pound apothecary): Used in pharmacies and pharmacology. It is currently equivalent to 373.2417 grams.
 The Castilian pound: It was used by the Spanish empire and its overseas colonies. It currently equals 469.093 grams.
 The Castilian Pharmaceutical Pound: Used in Spanish pharmacies and pharmacology. It currently equals 345.06975 grams.
 The Catalan pound: Used in the Catalan territories. It is currently equivalent to 400 grams.
 The Zaragozan pound: Used in the Zaragoza territories. It is currently equivalent to 350 grams.
 The Guipúzcoana pound: Used in the territories of Guipúzcoa. It currently equals 492 grams.
 The Neapolitan pound: Belonging to the ancient “Kingdom of Naples”. It currently equals 320.759 grams.
Relationship between “pounds” and “kilograms”
Currently the units of the “international system” and the “imperial system” coexist to this day. Most of the countries of the world use the units of the “international system”. An important part of this system are the units of measurement that are used in science. In the areas of knowledge related to physics, a special abbreviation is used with the acronym “MKS” which means “MetersKilogramsSeconds“.
However, the United States of America, Liberia and Burma officially use the “Imperial System”. The United Kingdom has officially used the “International System” since 1973, because it became part of the European Economic Community.
In September 1999, the National Aeronautics and Space Administration (NASA) carried out a mission to the planet Mars called “Mars Climate“.
This project consisted of placing a probe in orbit around Mars to study its atmosphere and surface. The probe was a joint project between two large propulsion laboratories; one of the laboratories was the “Jet Propulsion Laboratory” in Pasadena, California, which used units of the “International System” (meters and kilograms) for all their calculations.
However, the other laboratory, belonging to the company “Lockheed Martin Astronautics” located in Denver, Colorado used the “Imperial System” for its calculations (feet and pounds). As a result, after starting the mission and finding itself in an orbit position with Mars, the probe did not have a correct reading of its position, weight, and acceleration, which made it impossible for it to enter the planet’s orbit correctly. The angle of entry was wrong and the probe ended by impacting on the surface of Mars. The engineering teams had completely forgotten to transform the units from one system to another, so that the probe had a unit reading in all its sensors, which would have guaranteed the success of the mission.
The anecdote continues to be one of the most shameful cases in the history of the exploration of our solar system and a clear example of the conflict that is part of the relationship between the different measurement systems.
Precisely the problem between both systems is their conflict. There is no 1: 1 (one to one) relationship between the units of both systems (only the time in seconds is assimilated with the same magnitude between both systems).
We cannot establish a relation of a “pound” = “kilogram”. Even more complicated is that the relationship between the two units is not even equivalent in whole numbers.
The differences between both units of mass is very remarkable.
One (1) pound is approximately a little less than half the weight represented by a kilogram (½ Kg).
Taking this comparison, we can say that one (1) kilogram contains a little more than the value of weight represented in the mass of two (2) pounds.
To measure the mass of an object, the “Imperial System” uses the pound (lb or lbs). We can say that a pound equals 0.453592 kilograms in the “International System”.
Similarly, we can say that a kilogram is equivalent to 2.20462 pounds.
Converting from “pounds” of weight to “kilograms”
Formula to convert from “pounds” to “kilograms”:
1 kilogram (kg) = 2.20462 pounds (lbs)
Suppose you are going to buy a basket of apples.
The store manager informs you that the apples in the basket weigh approximately 30 pounds, however you need to know the weight in kilograms to follow a recipe.
You would need to convert or translate that weight in pounds to its equivalent weight in kilograms. For this calculation we will take the following relationship:
2.2 pounds (lbs) equals 1 kilogram (kg)
Therefore, we would have to divide the weight of the basket (30 lbs) by the ratio we have established from pounds to kilograms (2.2 lbs).
The result would be approximately 13.6363 kilograms (kg). If we “round” or “approximate” their decimals, we would obtain approximately 14 kilograms of apples.
This means that 30 Pounds (lb) of apples, roughly equal to 14 kilograms (kg)
Facilitation of conversion calculation
The present cases of conversion between pounds of weight and kilograms can be extremely confusing, even using mathematical formulas. You may wonder how do I know when to divide by kilograms or pounds to convert to the unit I want?
The answer is supported by mathematics.
Taking the example of apples: If you want to convert an object’s weight in pounds to kilograms, you need to divide by the respective value of pounds that equals one kilogram (2.20462 Pounds).
We can establish the following relationship: pounds x kilograms / (2.20462 pounds) = weight in kilograms.
kilograms x pounds / (0.453592 kilograms) = weight in pounds
In mathematical terms: the divisor of the equation will always be eliminated with its pair in the dividend (If you divide by kilograms (kg), the result will be reflected in pounds (lb); if you divide by pounds (lb), the result will be reflected in kilograms (kg).
Practical examples using “pounds” and “kilograms”
Perhaps you may wonder: What practical examples can currently be applied both to pounds of weight and to kilograms? Why are these conversions necessary? Here are several examples of the use of both systems:
The pound is also related to products produced in the United States. This implies that in that country, you can find pounds in products such as: food, textiles, shoes and clothing to mention a few specific examples.
Study of the “pound” and its derived units:
For its part, the pound of weight (lb) is made up of the units: grain (gr), drachma (dr), and ounce (oz). Of the previous three units, the most used commercially is the ounce (oz). One pound contains sixteen ounces (1 pound = 16 oz). There are several units of mass greater than the pound that belong to the same “Imperial System”. We define them below:
 The “grain” (gr) equivalent to 0.000142857 pounds (1 gr = 0.000142857 lb)
 The “drachma” (dr) equivalent to 0.00390625 pounds (1 dr = 0.00390625 lb)
 The “ounce” (oz) equivalent to 0.0625 lb (1 oz = 0.0625 lb)
 The “stone” (st) equals fourteen pounds (1 st = 14 lb).
The “arroba” is equivalent to 25 pounds (1 arroba = 25 pounds).
 The “short quintal” (US ctw) equivalent to one hundred pounds (1 US ctw = 100 lb)
 The “long quintal” (UK ctw) equivalent to 112 pounds (1 UK ctw = 4 = 112 pounds)
 The “short quarter” (US qtr) equivalent to 20 arrobas or 500 pounds (1 US qtr = 20 arrobas = 500 lb)
 The “long quarter” (UK qtr) equivalent to 5 long quintals or 560 pounds (1 UK qtr = 5 UK ctw = 560 lb)
The “short ton” (US ton) equivalent to 4 short quarts (4 US qtr) or 2000 pounds (1 US ton = 4 US qtr = 2000 lb)
 The “long ton” (UK ton) equivalent to 4 long quarts (4 UK qtr) or 2,240 pounds (1 UK ton = 4 UK qtr = 2,240 lb)
In order to make correct use of the mass units of the imperial system, it is necessary to know how to correctly carry out the conversions between their units.
In this case, we will take the most commercial units used today, which are: the ounce, the stone, the quintal and the ton.
Next we will develop a list of equivalences, based on the previous paragraph, in which we will develop the equivalence of these units with the pound:
 1 pound = 16 ounces (oz). Turn (1 oz = 0.0625 lb)
 1 stone = 14 pounds (lb). Turn (1 lb = 0.0714 lb)
 1 short quintal (US ctw) = 100 pounds (lb). Turn (1 lb = 0.01 US ctw)
 1 long quintal (UK ctw) = 112 pounds (lb). In turn (1 lb = 0.0089 UK ctw)
 1 short ton (US ton) = 2000 pounds (lb). In turn (1 lb = 0.0005 US ton)
 1 long ton (UK ton) = 2,240 pounds (lb). In turn (1 lb = 0.0004464 UK ton)
Examples of comparison with everyday objects
We can associate the weights with common objects of our day to day.
A good example is the food we buy at the market. Did you know that an apple weighs approximately 250 grams? This would mean that if you buy a kilogram of fresh apples, you would be buying approximately four (4) apples.
In the same way, if you buy two apples that weigh 250 grams each, you would be buying a little more than a pound (500 grams) of weight in apples: 1 Pound (lb) = 453,592 grams (g).
Another example we can take when buying liquids.
A liter of drinking water is equivalent to a kilogram of weight and as we have seen previously, a kilogram is equivalent to 2.20462 pounds (1 liter = 1 Kg = 2.20462 lb).
Milk, due to its density, the product of its chemical composition, has an approximate weight of 1.030 kilograms (kg) per liter.
Problems between conversions
The conversion between units of mass of different systems is not precise. As we have explained, the relationship between pounds and kilos is not comparable to a linear system or a onetoone (1: 1) relationship. The result of the conversions between both units always results in magnitudes that contain a large number of decimal places. Let’s look at several examples:
Certainly the lost percentage is not much, but when calculating large figures it can be very damaging.
Only by converting the same weight between different units, we have added 0.006 kilograms (0.6 grams = 600 milligrams) to the original weight.