In typeface design, the overshoot of a round or pointed letter (like O or A) is the degree to which it extends higher or lower than a comparably sized "flat" letter (like X or H), to achieve an optical effect of being the same size; it compensates for inaccuracies in human visual perception.
For example, the highest and lowest extent of the capital O will typically exceed those of the capital X. Although the extent of overshoot varies depending on the design and the designer, perhaps 1% to 3% of the cap or x-height is typical for O. Peter Karow's Digital Formats for Typefaces recommends 3% for O and 5% for A.
Similar subtle adjustments to create an even appearance occur in other fields. For example, in the game of go, the stones, which are black and white, are of slightly different sizes (black slightly larger), to give the appearance of being the same size.
- Frere-Jones, Tobias (9 April 2015). "This Optical Illusion Tricks You Into Thinking That Typeface Letters Are the Same Height". Slate. Retrieved 9 April 2015.
- Moore, Ian. "Making Geometric Type Work". Typographica. Retrieved 2 February 2016.
- Heidrun Osterer; Philipp Stamm (8 May 2014). Adrian Frutiger – Typefaces: The Complete Works. Birkhäuser. p. 333. ISBN 978-3-03821-260-7.
- Evans, Poppy; Sherin, Aaris. The Grapic Design Reference + Specification Book. USA: Rockport Publishers. p. 28. ISBN 978-1-59253-851-5.
- "Glossary of (some) typographical terms".
- Peter Karow. Digital Formats for Typefaces. p. 26. ISBN 978-3-642-78107-0.
- Devroye, Luc. "Hoefler & Frere-Jones". Retrieved 21 January 2015.