Em Dash Fraction of Em Lookup
Measured em dash advance/em ratio; Unicode does not impose one font-independent width.
Description
Convert a measured em-dash advance to a fraction of the font em.
An em dash need not have exactly a one-em advance in every font. This calculator expresses a supplied measured advance relative to the font's em-square units.
When to use this tool
Convert a measured em-dash advance to a fraction of the font em. Use it when the input measurements and conventions below match the operation you need.
- Prepare measuredGlyphAdvanceUnits, unitsPerEm, respecting the measurement basis and boundaries below.
- Compare the worked example with your intended operation before reusing its result.
How to use the tool and how it works
- Enter every field in the input table using the stated units and exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
For a nonnegative measured advance and positive unitsPerEm, the tool returns measured advance divided by unitsPerEm.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| measuredGlyphAdvanceUnits | Measured glyph advance units. | Finite number; zero or greater |
| unitsPerEm | Units per em. Em units. | Finite number; greater than zero |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.measuredFractionEm | Measured fraction em; use the stated units and sign convention. |
{
"input": {
"measuredGlyphAdvanceUnits": 250,
"unitsPerEm": 1000
},
"output": {
"result": {
"measuredFractionEm": 0.25
}
}
}Limitations and assumptions
- The result is a metric ratio, without glyph loading or visual inspection. It does not certify a font's typography or account for fallback and shaping.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Compare the metric calculation with the intended font and rendered text. Font shaping and layout inspection are more appropriate when the task depends on actual glyph positions or reading conditions. Compare the scope of the nearby tools below before substituting one.
References
Similar or alternative tools
- En Dash Fraction of Em Lookup
Measured en dash advance/em ratio; Unicode does not impose one font-independent width.
- Hair Space Fraction of Em Lookup
Measured hair space advance/em ratio; Unicode does not impose one font-independent width.