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

SetMapMode function (wingdi.h). Microsoft.
Glossary (VBA). Microsoft.
DPI and device-independent pixels. Microsoft.
SignedTwipsMeasureType.Val Property. Microsoft, quoting ECMA-376.
PageSize Class. Microsoft, quoting ISO/IEC 29500.
CHARFORMATA structure (richedit.h). Microsoft.
TextBox.Left property (Access). Microsoft.
NINCH and EMU. Microsoft, archived MSDN blog, 2011.
NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically. NIST.
Handbook 44 – 2026, Appendix C: General Tables of Units of Measurement. NIST, 2026.
Just How Small Is "Nano"?. National Nanotechnology Initiative.
Cocoon microstructures through the lens of topological persistence. Raichenko et al., Journal of the Royal Society Interface, 2024.

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