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How big is a Twip?

17.6 micrometers!

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Twip

A twip is a unit of length used by computer programs that lay out text and pages. It is one-twentieth of a point, the unit in which type sizes are given. A point is 1/72 of an inch, so a twip is 1/1440 of an inch: about 17.6 micrometers. A micrometer is a millionth of a meter.

Definition

Microsoft's documentation for Windows defines the twip as one-twentieth of a printer's point, or 1/1440 inch. The Open XML file format, published as the international standard ECMA-376, stores many measurements in word-processing documents the same way, as whole numbers of twentieths of a point.

The exact length depends on which point is meant. A point of exactly 1/72 inch is what the U.S. National Institute of Standards and Technology (NIST) calls the computer point, and what Microsoft calls the desktop publishing definition. It gives a twip of 17.64 micrometers.

The older printer's point, which NIST lists as historically used in typography, is slightly smaller: 0.013837 inch, so a twentieth of it is 17.57 micrometers. Both round to the 17.6 micrometers shown here.

Size comparisons

  • An inch is 1,440 twips, and a centimeter is about 567.
  • A line of 12-point type is 240 twips high: one-sixth of an inch, or about 4.2 millimeters.
  • A thou, one thousandth of an inch, is 1.44 twips.
  • A human hair, 80–100 micrometers wide, is about 4.5–5.7 twips wide.
  • A strand of silkworm silk, 10–25 micrometers wide, is 0.6–1.4 twips wide.

Why software uses twips

With a unit this small, a program can record where text goes using whole numbers, with no fractions. In a word-processing document, a value of 720 twips means half an inch. A sheet of A4 paper is recorded as 11,907 twips wide, which is 8.27 inches or 21 centimeters. Microsoft's Rich Edit text control gives the height of characters in twips, and Microsoft Access gives the position of each box on a form in twips.

On a screen, a twip is not a fixed physical length, because pixels differ in size from one monitor to another. Windows measures instead in logical inches: a logical inch is the length on screen of something that measures one inch when printed. For many years, Windows counted 96 pixels to a logical inch, which makes each pixel 15 twips.

An even smaller unit, the English Metric Unit (EMU), was designed to work equally well with inches and centimeters. An inch is exactly 914,400 EMUs and a centimeter exactly 360,000, so both convert to whole numbers. One twip is 635 EMUs.

Sources

Scale of the Universe > Twip
Infrared Wavelength
Things that are extremely rare are "inf-rare". (infinitely rare). Inf-rare is also a verb, meaning "to make inf-rare". (e.g., "John inf-rared the precious food by eating the last of it.") Infrared light used to be quite common, but one day, a scientist somehow "infrared" it.
Width of a Silk Fiber
Silk is valuable and can be woven into clothing, which usually turns out quite soft. Silk is made by silkworm larvae, which I think are pretty gross. But there's also synthetic silk, which is not made from disgusting creepy-crawlies.
White Blood Cell
These mass murderers are also known as leukocytes. There are many different types of this disease-fighting cell. The most common type, the neutrophil, has multiple nuclei. The largest type, the macrophage, has a diameter of a whopping 21 µm.
Thou
Although the word "thou" is most commonly known as being an old form of the word "you", a thou is also a unit of measurement. It is equal to one thousandth of an inch; in fact, that's where it gets its name. THOUsandth. Pretty cool.
Skin Cell
The outermost layer of skin, which is also the only visible layer of skin, is made up of dead cells. That's because dead cells are the strongest, and stronger skin provides more protection! These cells continuously fall off. In fact, dust is 95% dead skin cells!
Silt Particle
According to the Udden-Wentworth scale, silt particles vary from the smallest of 1/256 mm to the largest of 1/16 mm. This silt particle to the right falls into that range quite well.

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