Several MathML presentation elements have attributes that accept length values used for size or spacing. MathML accepts different units and constants for specifying lengths.


Unit Description
em font-relative unit
ex font-relative unit. (The "x"-height of the element, 1ex ≈ 0.5em in many fonts)
px Pixels
in Inches (1 inch = 2.54 centimeters)
cm Centimeters
mm Millimeters
pt Points (1 point = 1/72 inch)
pc Picas (1 pica = 12 points)
% Percentage of the default value.


Constant Value
veryverythinmathspace 1/18em
verythinmathspace 2/18em
thinmathspace 3/18em
mediummathspace 4/18em
thickmathspace 5/18em
verythickmathspace 6/18em
veryverythickmathspace 7/18em
Negative contstants are introduced in Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4) (bug 650530)
negativeveryverythinmathspace -1/18em
negativeverythinmathspace -2/18em
negativethinmathspace -3/18em
negativemediummathspace -4/18em
negativethickmathspace -5/18em
negativeverythickmathspace -6/18em
negativeveryverythickmathspace -7/18em

Note: Namedspace binding is deprecated in MathML3 and has been removed in Gecko 15.0 (Firefox 15.0 / Thunderbird 15.0 / SeaMonkey 2.12) (bug 673759).