An MIT Touch Lab study of Human Fingertips to investigate the Mechanics of Tactile Sense found that the average width of the index finger is 1.6 to 2 cm (16 – 20 mm) for most adults. This converts to 45 – 57 pixels, which is wider than what most mobile guidelines suggest.
1. Designing for 34 / 44 pixels touch target (Windows Phone UI Design and Interaction Guide and iPhone Human Interface Guidelines)
2. Designing for 57 pixels touch target (ergonomically correct)
3. Designing for 72 pixels touch target (Thumb correct)