Who invented the Inch? (Invention Timeline Explained)

Measurement is one of the fundamental concepts of life. Scientists use precise measurements to conduct experiments, calculate the correct dosage for medicines, and formulate different theories. Accurate measurement is also essential in engineering, manufacturing, farming, and architecture. On the other hand, a measurement error can lead to unfortunate events – a wrong dose can kill a patient, a mismatched part can crash an aircraft, or a miscalculated plan can wreck a whole building.

We are fortunate to follow a standard unit of measure known as the Standard Systems of Units or SI system. I bet you’ve heard of it before. Units like kilograms, meters, and liters are all part of it. Almost everyone in the world uses the SI system except the USA, which still uses the English system. One of the units from the English system is “inch,” which measures length. This article explains the story behind the invention of the inch.

Who invented the inch?

The earliest written record of the use of the inch as a unit of measure was from the Laws of Aethelberhy in England in the early 7th Century. However, Edward II of England gave the first legal definition of an inch in 1324.

The inch’s key contributors (and evolution)

  • People of England
    First Written Record

    The earliest record of the use of the inch as a unit of measure. The reference was from the Laws of Aethelberht, which was documented in a manuscript entitled Textus Roffensis. 

  • Edward II of England
    First Legal Definition

    Back in 1066, an inch was the same size as three barleycorns (an Anglo-Saxon unit of length). Then, in 1324, Edward II of England made the first legal definition of an inch. His proclamation goes like this: “An inch is equivalent to three grains of dry and round barley, placed end to end, in vertical position.”

  • King David I of Scotland
    Scottish Inch 

    In an attempt to make a standard unit of measure, King David I of Scotland devised a practical way to size up an inch. He used the width of an average man’s thumb as the measurement of an inch.

  • Charles Butler and John Bouvier
    Inch vs. Barleycorn

    Charles Butler (1814) and John Bouvier (1843) argued that barleycorn (the Anglo-Saxon unit) was the base unit of the English Measure System. Butler based his claim on the old legal definition of an inch based on barleycorn. So, they both believed that barleycorn, not the inch, is the fundamental measure that is the basis for all other units.

  • Thomas Corwin
    The Mendenhall Order

    Thomas Corwin signed the Mendenhall Order in 1893, which defined the US inch as 25.4000508 mm and UK inch as 25.399977 mm.

  • Carl Edvard Johansson
    De Facto Standard

    In 1912, Carl Johanson built standard gauge blocks for an inch with a nominal length of 25.44 mm. His gauge block became the de facto standard or the industrial inch. By 1935, almost 16 countries had adopted Johanson’s ratio.

When was the inch invented?

The earliest written record of the use of an inch is in the Early 7th Century. However, Edward II of England legally defined it in 1324.

A brief history of the inch

Imagine building houses, roads, temples, and other infrastructure without a standard unit of measure. The whole process will be chaotic, and loads of errors will happen, especially since many people are involved in the construction. However, ancient people were smart enough to figure out that they needed a standard unit of measure. The invention of the unit inch proved the resourcefulness and intelligence of ancient people.

The earliest reference to the use of the inch was written in a manuscript from the 7th Century in England. The Laws of Aethelberht stated the fine for a wound is based on its depth: one shilling for an inch-long injury, two shillings for two inches, etc.

Different references from the 10th Century talked about an Anglo-Saxon unit of length called barleycorn. Basically, “barleycorn” is a unit of measure based on a dried piece of barley. This is smart since barley is one of the earliest and most common grains cultivated by humans. Since barley is present almost anywhere, people back then could easily find dried barley for reference.

In 1324, Edward II of England gave the first legal definition of an inch. He described it as the equivalent of three round and dried barley grains laid end to end. People have used this definition for many years. Scholars came across similar references from the Laws of Hywel and Ancient Laws and Institutes of Wales.

Pieces of literature point out King David I of Scotland for writing his definition of an inch in his work Assize of Weights and Measures. Instead of barley or grains, he used a more common reference, which most people possess and bring all the time – thumb. According to King David I, the width of a person’s thumb is the same length as an inch.

In later years, debates about the base unit of the English Measure System arose. Many experts and scholars participated in the discussion. In 1814, Charles Butler, a Mathematics professor, argued that barley was the base unit. His claim was based on the premise that the definition of an inch was anchored to the concept of the barleycorn. John Bouvier also agreed to Butler’s claim. However, he also observed that barleycorn has no definite length, so it’ll be impossible to calculate the standard measure of an inch. 

George Long also pointed out the endless errors and inaccuracy of estimating the standard measurement of an inch using barley. In addition, variables like barley variety, evolution, and grain size differences can make the study difficult to complete.

It was in 1893 when Thomas Corwin signed the Mendenhall Order. Because of this, the USA settled the issue. It effectively defined the US inch as 25.4000508 mm and the UK inch as 25.399977 mm, which are very close to the standard inch we are using nowadays.

In 1912, Carl Edvard Johansson built gauge blocks. These blocks serve as standard patterns for other manufacturers. His contribution is a massive step toward the standardization of measurement. He considered the US and British inch values and decided to compromise after careful study. He built the gauge block for an inch with a value of 25.4 mm.

Many countries adopted Carl Johansson’s gauge block. They call his calculations the “industrial inch,” used by manufacturers in different places of the world. By the end of 1935, 5 years after their release, 16 countries were using and promoting Johansson’s block.

The inch timeline

  1. 7th Century
    Laws of Aethelberht

    The British followed the Laws of Aethelberht back in the 7th Century. Scholars found a section from this set of laws that mentioned the word “inch.” 

  2. 10th Century

    Barleycorn, an Anglo-Saxon unit of length, was used in several references to describe the size of an inch. One inch is equivalent to 3 barleycorns.

  3. 1324
    Ancient Laws

    Many references from ancient law also describe an inch’s legal definition. For example, Sir Edward II of England described it as having the same length as three dried barley grains.

  4. 1800’s
    Dethroning the Inch

    Back in the 1800s, many scholars believed that barleycorn should be considered as the base unit of the English Measure System and not the inch.

  5. 1912
    Carl Edvard Johansson

    Carl Johansson set the ratio for an industrial inch at 25.4 mm. He made gauge blocks other manufacturers can use as a standard measure for inches. 

Where was the inch invented?

England has the earliest record of an inch used as a unit of measurement. The document dates back to the 7th Century when a law described the punishment for wounds depending on the depth (in inches).

The importance of the inch

  • For display screens

    The inch is generally used to measure smaller objects like the length of a pen. Japan and Europe prefer to use inches to measure electronic parts and display screens.

  • Easy references

    We don’t carry a ruler with us all the time. So, we can’t always measure things by centimeters. But there are plenty of things around us that measure precisely or close to an inch which we can use as references. For example, you can use a quarter, paperclip, hockey puck, and two kittles.

  • Pricing artworks

    It’s tough for artists to put price tags on their artworks. Do they consider the canvas used? The type of paint? Artists have different opinions regarding this matter. For some it’s too pricey, others think it’s too cheap! So, artists created a more consistent system by calculating the cost by the square inch. 

  • For learning fractions

    Some educators use the concept of an inch when discussing fractions. This is good since they can visualize it using the ruler.

The inch by the numbers

  • 2There is a 2 millionth difference between the “industry inch” and the original “US inch.” This measures ⅛ of an inch per mile. This slight difference won’t gravely affect shorter distances. However, the 2 millionth difference can affect coordinate values.
  • 8Although we already have a standardized unit of measure, there are still slight differences between countries. For example, the voet or Amsterdam’s foot is 8% shorter than the British.
  • 2.54Most parts of the world use the Metric system. The inch is part of the English Measure System. So, often, you’ll need to convert inch to centimeter. It’ll be handy to know that 1 inch is equal to 2.54 centimeters.
  • 12In some references, an inch was also described as equal to the combined measure of 12 poppyseeds.

Five facts about the inch

  • Used in Sports

    The inch is used to set specific measurements for sports equipment. The sword or foil used in fencing measures 41.33 inches. Most tennis racquets measures from 27 to 29 inches.

  • Standard size

    A ruler is just one of the things that a student should have, and the standard size of a ruler is 1 foot or 12 inches long. 

  • Ouchie needle

    Most children are scared to be vaccinated. Even adults are afraid when seeing a syringe. We imagine it to be long and scary. But do you know that the standard size of a syringe needle is just 1 to 1.5 inches?

  • Random 1 inch

    Do you know that a paper clip, a bottle cap, a sewing pin, a bolt, and a Canadian $1 coin diameter are all 1 inch? 

  • Different types of inch

    The term inch is subdivided into different types: halves, eights, sixteenths, and quarters.

FAQ about the swim fins

  • What is the symbol for inch?

    The symbol for inch is the double prime (‘’), or it can also be “in.”                                                                                                                                                                                                                                                         

  • What is an inch?

    An inch is a unit of measure for length and is used in British imperial and US customary systems. 

  • Why do American use inches?

    Americans chose to use the English measurement system to make it easier for them to communicate measurements. It’s like using lingua franca to avoid misinterpretations and miscommunications.

  • What is the equivalent of an inch?

    The exact equivalent of an inch is 25.4 millimeters, 39.37 inches in 1 meter, 12 inches in 1 foot. 

  • Why is it called inch?

    The word inch came from the old English word ynce or ince, from the Latin word unica which means one-twelfth of a Roman foot. 

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