Convert Inches to Millimeters
Inch (in) to Millimeter (mm) typography conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 in = 25.4 mm
1 Inch = 25.4 Millimeters
1 Millimeter = 0.039370079 Inches
1 in in every supported unit
Conversion chart: Inch to Millimeters
Conversion table
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.01 in | 0.254 mm |
| 0.1 in | 2.54 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 20 in | 508 mm |
| 50 in | 1270 mm |
| 100 in | 2540 mm |
| 1000 in | 25400 mm |
Inch (in)
Definition: The imperial unit of length equal to exactly 1440 twips, 72 computer points, or 6 picas — the reference unit the entire twip/point/pica system is ultimately built around.
History: Standardized to exactly 25.4 millimeters internationally in 1959, though its use in print and page layout goes back centuries as the traditional English unit of small-scale measurement.
Current use: The most common physical unit for describing page sizes (US Letter is 8.5 × 11 inches) and is the direct basis for the modern point (1/72 inch) and pica (1/6 inch).
Millimeter (mm)
Definition: One thousandth of a meter — a finer metric length unit useful for precise print margins and small typographic offsets.
History: A standard SI-prefixed submultiple of the meter, used throughout metric-system engineering and design specifications.
Current use: Common in print-shop and packaging specifications where margins, bleeds, and trim marks are given in millimeters rather than points or inches.
Supported Units
| Unit | Symbol | In Twip |
|---|---|---|
| Twip | twip | 1 twip |
| Meter | m | 56692.913 twip |
| Centimeter | cm | 566.92913 twip |
| Millimeter | mm | 56.692913 twip |
| Character (X) | char (X) | 120 twip |
| Character (Y) | char (Y) | 240 twip |
| Pixel (X) | px (X) | 15 twip |
| Pixel (Y) | px (Y) | 15 twip |
| Inch | in | 1440 twip |
| Pica (Computer) | pica | 240 twip |
| Pica (Printer's) | pica (pr) | 239.10336 twip |
| PostScript Point | pt (PS) | 20 twip |
| Point (Computer) | pt | 20 twip |
| Point (Printer's) | pt (pr) | 19.92528 twip |
| En | en | 9.9626401 twip |
About These Parameters
- Value
- The typographic measurement you want to convert, expressed in the "From" unit — a font size in points, a margin in inches or millimeters, or a layout coordinate in twips.
- From Unit
- The unit your value is currently measured in — an RTF document's twip coordinate, a font size in computer points, or a physical page dimension in inches or centimeters.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly, handy when moving between a print-trade unit like the pica and a physical unit like the inch.
How Typography Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the twip. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Inch → Millimeter: multiply by 25.4. For example, 1 in × 25.4 = 25.4 mm.
Points and Picas: From Metal Type to Digital Type
Before desktop publishing, printers worked in the Anglo-American point system standardized by 19th-century type foundries, where a point measured roughly 1/72.27 of an inch and a pica was 12 of those points. When Adobe introduced PostScript in 1982, it rounded the point to a much cleaner exactly 1/72 of an inch — the "computer point" (and computer pica, exactly 1/6 inch) used by virtually every modern design and word-processing application. The tiny difference between the two (about 0.3%) rarely matters for everyday layout work, but this converter keeps both available since historical typesetting records still use the older printer's point and pica.
Why Windows and RTF Use the Twip
Microsoft introduced the twip for Windows' GDI graphics subsystem and the Rich Text Format in the 1980s specifically because 1/1440 of an inch is small enough to place text and graphics with sub-pixel precision while still being a whole number for almost any practical page coordinate — a working unit that avoids the rounding errors floating-point point or pica values would introduce into a document's internal layout data. That's why RTF files and Windows layout APIs still store every coordinate in twips today, even though no one designs directly in twips the way they think in points or inches.
Example
1 in equals 25.4 mm. For scale, a standard 12-point font size is exactly 240 twips, a 1-inch page margin is 1,440 twips (or 6 computer picas), and US Letter paper (8.5 × 11 inches) measures 12,240 by 15,840 twips.
Frequently Asked Questions
How many Millimeters are in 1 Inch?
1 Inch (in) equals exactly 25.4 Millimeters (mm).
What is a twip and why does it matter?
A twip ("twentieth of a point") is 1/1440 of an inch — small enough for precise text and object placement, yet still a whole number for nearly any practical layout coordinate. It's the native internal unit of RTF documents and the Windows GDI graphics subsystem, so converting to and from twips matters whenever you're working with document layout data programmatically.
What's the difference between a computer point and a printer's point?
The computer (PostScript) point is exactly 1/72 of an inch, standardized by Adobe in 1982 for digital typesetting. The older printer's point, from the metal-type era, is about 1/72.27 of an inch — very slightly smaller than 1/72. The difference is under half a percent, but it's why historical typesetting measurements don't translate exactly onto modern digital point sizes.
How many points are in a pica?
A pica is always 12 points — this ratio holds for both the computer pica/point pair (12 × 1/72 inch = 1/6 inch) and the older printer's pica/point pair (12 × ~1/72.27 inch), so as long as you don't mix the computer and printer's versions, the "12 points per pica" rule always applies.
Are the character and pixel units exact?
No — character units are an approximation based on average character-cell size in a monospaced font, and the pixel units here assume the traditional 96-dots-per-inch Windows screen convention (1440 twips per inch ÷ 96 pixels per inch = 15 twips per pixel). Actual character widths vary by font, and actual screen pixel density varies by display, so treat these two as legacy approximations rather than physically exact measurements.