How correctly to translate inch in mm? How many mm in inch?

And remember a little girl from a fairy tale, Thumbelina? Never thought of the origin of her name? Let's talk about this.

About the word "inch"

Translated from the Dutch word "inch" means "thumb." This is a measure of length equal to the width of the thumb of the average person (although some say that it is the length of his upper phalanx). But, no matter what part it was, it turns out that Thumbelina is a girl the size of a finger.

By the way, in the fairytale epic one more hero of the same size is known. It turns out that our beloved Boy-with-Palchik could also be called Thumbler by analogy. A joke, of course. However, the fingers of people are different, so I would like to clarify: how many mm in inch?

About the size of an inch

Determining what an inch is in mm is not so simple. The fact is that this unit, which for hundreds of years, has repeatedly changed even within the limits of one system of measures, not to mention different ones. The Viennese inch was 2.6340278 cm, or 26.3 mm; In Spain, the local inch (pulgada) was 23.2 mm; In Mexico, where it was also called pulgada, the size of an inch in mm was approximately 23.3.

This list can be replenished almost to infinity. Each of the German lands had its own, different from the others, the mentioned measure of length: Baden, Bavarian, Saxon and Prussian, and also an inch of the Rhine union. In the provinces of Ostsee, respectively, were Courland, Riga and Reval. In the territories of the Polish-Lithuanian Commonwealth there were Old Polish and New Polish inches, as well as Wroclaw, Breslau, Silesian, old Lithuanian. France had its own measure of length. There were similar units even in Japan and China. So, 1 tsun (Chinese inch) in mm was 33.3. There is also the so-called Vidiconian inch, which is most often used when measuring the matrix of a digital camera. It is equivalent to 16.93 mm.

About the Metric Convention and metric system of measures

May 20, 1875 in Paris, in the building of the Ministry of Foreign Affairs of France, was signed the so-called. The Metric Convention is a treaty designed to ensure uniformity of international metrological standards. To this agreement, Russia joined - on behalf of the emperor, the agreement was signed by Okunev, an embassy adviser. The adoption of the convention served as an important impetus in the development of the metric system of measures and the beginning of the development of the standards of meter and kilogram. Later, basic units of quantities were introduced in the areas of electricity and optics. More than 50 countries have joined the Metric Convention, including all the most developed countries.

Two important remarks. First: an inch is an obsolete unit, generally unrelated to the metric system. Moreover, OIML (International Organization of Legal Metrology) strongly recommends its early withdrawal from circulation where it is still used for measurements (the reason, I think, is understandable). The second remark. The largest and most highly developed country in the US, although it signed the Metric Convention, still does not consider it necessary to use the metric system of measures. Inch is widely used as a local unit of measurement, which in the rest of the world seriously complicates the adherence to OIML recommendations.

About English inch

So what does this unit still represent, how to express 1 inch in mm? At present, when mentioning this term, as a rule, we mean the English, or imperial measure of length. Its magnitude has also changed many times, but since 1958, the translation of inches in mm will yield a result of 25.4 per unit. So the size of our fabulous characters would now be 2.54 cm. Indeed, crumbs!

Incidentally, in England an inch is called inch, its generally recognized sign is quotes: for example: 17. "So a person who decided, say, buy a TV should not be confused by a double stroke or a mention in the next to the figure that characterizes the screen size. The same SI units.

In the US, as in England, since 1958, an inch is considered equal to 2.54 cm. There, this unit is used in different spheres, and quite widely - for example, when indicating the caliber of small arms. In America, the weapons caliber (internal diameter of the barrel) is measured in hundredths of an inch. Accordingly, the famous Colt 45 gauge means a weapon with a barrel diameter of 0.45 inches (11.43 mm).

Where is used in.

A legitimate question arises. Why does a person living in a country where the metric system of measures (Russia) is used should worry American length indicators or, say, how to convert mm to inches? But it's not so simple. Recently, due to the expansion of American technology and the emergence of new technical terms, inches have become used in Russian much more often. Yes, and before, there were entire industries, where the mentioned value was considered the basic unit of measurement. Thus, in inches it is customary to measure the calibres of artillery pieces. True, this should be dealt with separately. For example, in the UK, unlike the US, the calibers show a thousandths of an inch. A famous Russian "trilinear" - this is the 3 mentioned units (7.62 mm).

Inches are also used in the automotive industry: they measure the diameters of the wheel disks of a car. Since the existence of the Soviet automobile industry began with foreign technologies and licenses, foreign terminology was also used to a large extent. For example, one of the first-born of the domestic automotive industry, KIM-10, had a cylinder diameter of 2 1/2 "(or 63.5 mm) .In inches, the diameters of telescope objectives are also indicated, and this unit is also used for marking pipes.

About pipe inch

A long tradition is the use of the value in question when working with gas and water pipes, as well as for marking threads cut on them. But it should be noted: the pipe inch in mm is not the same as the usual inch.

This concept can not be called scientific, and yet it has a strictly defined meaning. A pipe inch is considered to be the outer diameter of such a pipe, in which the inner diameter corresponds to the usual inch. This value is somewhat conditional: the pipes have different thicknesses, which, of course, affects the ratio of diameters. And yet, to some uniformity in this matter came.

About the conditional pass

Speaking about the parameters of manufactured (rolled) pipes, they usually mean their diameter from the outside. Of course, with the same external values, but with different wall thicknesses, the internal dimensions of different products may differ significantly. Therefore, the concept of conditional passage of a pipe is introduced: it is a special internal diameter, to which a certain external value can correspond. For example, in a pipe with a passage of 40 mm, the actual internal diameter can be represented by any sufficiently close number.

Why do you need to know this? Then, that the main indicator by which the passage of water is calculated is the inner diameter of the pipe. And in tap water use products like steel, marked in inches, and copper, aluminum, made of stainless steel, produced by metric standards. Therefore, the correct translation is necessary: inches in mm of pipe (reference of the value to metric values). There are special tables (GOST 3262-75), which establish the correspondence between different types of pipes and their parameters. In them, as the base, the value of the conditional diameter (passage) of the pipe is taken.

About the Threads

Pipe often enough to connect. Diameters larger than 6 inches usually use welding, smaller products are twisted by thread, the parameters of which are usually expressed in inches. Pipe thread pitch is the number of threads placed on one such unit. There are also tables of thread pitch matching in mm thread count per inch. There is also a more generalizing table, connecting the inch dimensions of a cylindrical pipe thread with its metric parameters. In accordance with it, in particular, a 3-in.-Mm thread corresponds to 87,884; 86,405 and 84,926 (nominal values of external, average, internal diameters, respectively). In general, pipe threading is a whole science plus a considerable group of different standards whose aims are the correct connection of elements and structures having threads. At the heart of these standards are the indicators of the inch system of units.

And again about inches

The name "inch" and its derivatives can often be found in the description of other production processes. For example, under the word "inch" is sometimes understood as a board in the thickness of an inch or the same length of a nail (in these cases, the translation of inches in mm again becomes actual). But that's not all. Until now, the term "inch" is popular when mentioning fasteners and many other metal products. And yet, this word would be considered anachronistic, if not for the rapid development of computer technologies that brought new terms into our circulation. The resolving power of printers and some other devices is usually indicated in dots per inch (dpi). There is also the concept of pixels per inch (ppi), used when specifying the resolution of the device that introduces or displays graphics. The concepts of dpi and ppi are technologically not identical to each other.

In inches, also measure the screens of mobile phones, monitors, diagonals of TVs (formerly in the USSR, this value was expressed in cm). About screens it is necessary to talk a little more in detail.

About pixels and image

Many, arguing about television or other screens, consider the most important indicator of its size. They are strenuously translating the length of the diagonal (say, 21 inches in mm) into more familiar measures, trying to figure out if this value is sufficient for them. At the same time, there are indicators not less important, which buyers of such equipment sometimes do not pay attention.

Pixel is a technical term that has migrated to everyday life. If you move away from complex definitions, then the pixel can be called the smallest indivisible image object of a certain color. A raster picture of computers is a collection of pixels arranged in rows and columns. The principles of television are somewhat different, but here it is also customary to talk about the resolving power of a device, that is, its ability to display the largest number of details (units) of a displayed image. Of course, any image is more beautiful and qualitative, the higher the number of pixels per unit of screen area. This is the already mentioned indicator ppi (the number of dots per inch of the display). The value of ppi is extremely important for obtaining a bright clear quality picture, so it must certainly pay attention when buying the appropriate equipment.

However, not only in pixels happiness - so, at least, say many experts. The pursuit of high resolution leads to a serious increase in the load on graphics cards. That is, buyers of television and other similar equipment should carefully weigh the pros and cons and stop at the optimal version for the device.

Inches, inches ...

In computer practice, we remember this value even when we update the parameters of hard drives, disk drives, and DVD drive characteristics. In inches, indicate the size of the matrix of digital cameras. What is the matrix and how does its size affect the quality of the images? This is a very interesting and important question, but for another discussion.

How to remember the size of an inch?

A person who does not have a good memory for numbers should know the following: 4 inches in mm will be 2.54 * 4, i.e. little more than 1 cm. In cases where special accuracy is not needed, such a scheme can be used in some Household situations.

Conclusion

If you write a query in any search engine "inch", then the answer to the story of James Aldridge "Last inch" will certainly turn out to be. This small but really worthwhile work, which has become a classic of world literature, is not once filmized. A deeply tragic story about human courage, a complex relationship between father and son, the fads of fate.

But the story's interesting. Why the "Last inch"? According to the plot, a ten-year-old child, who had never before ruled an airplane, managed not only to drive a complicated route, but also to plant it under heavy and even dangerous conditions. The child coped. The last inch before landing became a frontier, turning him into another person - an adult, responsible, he also highlighted a new facet in the future relationship of father and son. So it's not always right to express an inch in mm - sometimes this value requires completely different approaches and equivalents.