Typography Converter
Convert points, picas, pixels, ems, Didot points and ciceros — where the modern point is exactly 1/72 inch but the American, Didot and TeX points are all different sizes.
Typography Converter
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Point size describes the type body, not the height of any letter; cap height and x-height vary by typeface.
- The CSS reference pixel is a fixed 1/96 inch and does not describe physical device pixels on high-density screens.
- Historical point values are the standardised figures and do not capture variation between individual foundries.
In short: Modern typography is exact: the DTP point is precisely 1/72 inch, twelve make a pica, and the CSS reference pixel is 1/96 inch, so 1 px = 0.75 pt with no rounding whatsoever. The traps are historical. The American point of 1886 is 0.35146 mm, so 72 of them make 0.9963 inch, not one. The Didot point is 0.3760 mm because it derives from the French royal foot. And the em is not a fixed length at all — it is whatever the current font size happens to be.
Formula
Every modern typographic unit is an exact rational fraction of the inch. The American, Didot and TeX points are separate historical standards of genuinely different size, not roundings of the modern one.
Worked Example
- Convert to millimetres. 12 pt × 0.352778 = 4.2333 mm.
- Divide by the target factor. A CSS pixel is 0.264583 mm.
- Read the result. 4.2333 ÷ 0.264583 = 16 px, exactly.
- Check the ratio. 72 and 96 both divide the inch, so pt × 4/3 = px with no rounding.
- Treat em separately. It is a ratio to the font size, not a length.
Why 72 American points are not an inch. When the Type Founders Association standardised American typography in 1886, it did not adopt a clean sixth of an inch. It adopted the existing Johnson pica of 0.166044 inch, because most foundries were already cutting type to something close to it. That makes the American point 0.3514598 mm, and seventy-two of them measure 0.996264 inch — short of a full inch by about a quarter of a percent. The discrepancy survived for a century and only disappeared when PostScript redefined the point as exactly 1/72 inch in 1984. Old specifications and old metal type still carry the older measure.
Strengths & Limits Of This Model
Where this engine is strong
- Separates the exact modern units from the historical points instead of merging them.
- Handles em and rem as ratios requiring a font size, rather than pretending they are lengths.
- Shows the American, Didot and TeX equivalents side by side.
Where it stops
- Not a font metrics or typeface comparison tool.
- Does not model optical sizing or hinting.
- Cannot tell you how large a letter will actually look.
Practical Use Cases
Print to web handoff
Converting a print specification in points and picas into CSS pixels, where the 4:3 ratio is exact and needs no rounding.
Working with European typographic specifications
Didot points and ciceros appear throughout continental type history and in older French and German specifications.
Legibility and accessibility compliance
Minimum type sizes are often specified in points while implementation happens in pixels or rems.
Setting leading and measure
Line height as a percentage of type size, and column width in picas — pair with the Length Converter for page geometry.
Methodology & Editorial Standards
All conversions route through the millimetre, with the international inch fixed at exactly 25.4 mm. The DTP, PostScript and CSS point is exactly 1/72 inch; the pica is twelve of those; the CSS reference pixel is exactly 1/96 inch, making the pixel-to-point ratio exactly 3:4. The American point is derived from the 1886 Johnson pica of 0.166044 inch, giving 0.3514598 mm. The Didot point is taken as 1/864 of the French royal foot of 324.839385 mm, or 0.37597151 mm, with the cicero at twelve Didot points. The TeX point is exactly 1/72.27 inch, which is 800/803 of the PostScript point. The DIN and JIS quarter-millimetre point and the Imprimerie Nationale point of 0.4 mm are exact by definition. Em and en are deliberately excluded from the unit table because they are ratios to the current font size rather than lengths, and are handled in a separate card that requires an explicit font size. All conversion factors are exact by definition under the International System of Units, or exact by international agreement where the unit is defined by treaty. Values are held at full IEEE-754 double precision internally and rounded only for display, so chained conversions do not accumulate drift.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Typography Converter — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many pixels is 12 pt?
Exactly 16 px. The CSS reference pixel is 1/96 inch and the point is 1/72 inch, so one point is exactly 4/3 of a pixel and one pixel is exactly 0.75 pt. A 12 pt font is a 16 px font with no rounding at all, which is also why 16 px is the default body text size in every major browser.
Is a point always 1/72 of an inch?
Only since 1984. The PostScript point defined it that way and CSS inherited it, but the American point standardised in 1886 is 0.3514598 mm, so seventy-two of them come to 0.996 inch. The Didot point used across continental Europe is 0.376 mm, and TeX uses 1/72.27 inch. Four different points, all called points.
What is the difference between a pica and a cicero?
Both are twelve points, but of different points. A pica is twelve DTP points, so exactly 1/6 inch or 4.2333 mm. A cicero is twelve Didot points, which is 4.5117 mm — about 6.6 % larger. They are the same idea implemented in two incompatible measurement systems, one based on the English inch and one on the French royal foot.
What is an em and why is it not in the unit list?
Because it is not a length. An em is defined as the current font size, so one em is 16 px in 16 px text and 24 px in 24 px text. It moves with whatever it is applied to. That makes it excellent for padding that should scale with type and dangerous for anything that must stay fixed. A rem does the same relative to the root font size, which is why rem is usually the safer choice.
Why do print designers still use picas?
Because a pica is a convenient whole-number unit for column widths and margins in a way that inches and millimetres are not. A 24-pica column is cleaner to specify and scale than a 4-inch column, and the twelve-point subdivision aligns naturally with type sizes and leading. Six picas to the inch also makes mental arithmetic easy.
How do I convert points to millimetres?
Multiply by 0.3527778, since a point is 1/72 of 25.4 mm. Twelve points is 4.2333 mm and 72 points is exactly one inch. If you are working from an older European specification, check whether it uses Didot points instead, in which case the multiplier is 0.3759715 and the numbers come out about 6.6 % larger.
What is the right line height for a given type size?
Around 120 % of the type size is the common default, so 12 pt text takes 14.4 pt of leading. Extended body reading is more comfortable at 140 to 160 %, while display and headline type often works at 100 to 110 % because large letterforms need less separation. Wider columns need more leading than narrow ones.
Does a 72 pt font produce inch-tall letters?
No. At 72 pt the type BODY is one inch, which is the historical height of the metal block, not the height of any letter on it. The capital height of a 72 pt font is typically around 0.7 inch and the x-height perhaps 0.5 inch, and both vary considerably between typefaces. This is why two fonts at the same point size can look very different in size.