Why size matters
A fingertip's contact area is far larger than a cursor, and the finger hides the target at the moment of touch. Vogel and Baudisch (2007) called this the fat-finger problem and proposed a callout technique. Holz and Baudisch (2010) found systematic offsets between where users think they touch and what the device senses. Fitts's law alone therefore underestimates mobile errors; finger imprecision must be modelled separately (Bi et al., 2013).
How big is big enough
Parhi et al. (2006) reported errors rising below about 9.2 mm for one-handed thumb use, and Park and Han (2010) showed required size varies with location. Henze et al.'s (2011) analysis of 100 million taps confirmed larger errors for small targets and near edges. Platform guidelines settle on about 44pt (iOS) or 48dp (Android), while WCAG 2.2 (W3C, 2023) sets a 24×24 CSS pixel minimum (2.5.8) and a 44×44 enhanced level (2.5.5).
Spacing and placement
Spacing matters as much as size: tightly packed links cause neighbours to be hit even when each is large. WCAG 2.5.8 therefore allows an exception when 24px circles around targets do not overlap. Separate visual size from hit area, enlarge buttons outside the thumb zone or at corners, and keep destructive actions apart. This is especially important for people with tremor or low vision, making it central to web accessibility.
FAQ
- What is the minimum touch target size?
- WCAG 2.2 sets 24×24 CSS pixels as a minimum, and 44×44 (iOS 44pt, Android 48dp) or larger is recommended for comfortable use.
- What if the icon must stay small?
- Keep the artwork small but extend the tappable area with transparent padding.
Sources reviewed: 2026-10-27
References
- Parhi, P., Karlson, A. K., & Bederson, B. B. (2006). Target size study for one-handed thumb use on small touchscreen devices. In Proceedings of the 8th Conference on Human-Computer Interaction with Mobile Devices and Services (pp. 203–210). ACM. Often cited for errors levelling off around 9.2 mm; a basis for minimum sizes.
- Park, Y. S., & Han, S. H. (2010). Touch key design for one-handed thumb interaction with a mobile phone: Effects of touch key size and touch key location. International Journal of Industrial Ergonomics, 40(1), 68–76. Shows size and location interact, helping decide whether edge buttons need extra size.
- Vogel, D., & Baudisch, P. (2007). Shift: A technique for operating pen-based interfaces using touch. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 657–666). ACM. Tackles the fat-finger occlusion problem with a callout technique.
- Holz, C., & Baudisch, P. (2010). The generalized perceived input point model and how to double touch accuracy by extracting fingerprints. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 581–590). ACM. Reveals the gap between intended and sensed touch points, explaining touch offsets.
- Henze, N., Rukzio, E., & Boll, S. (2011). 100,000,000 taps: Analysis and improvement of touch performance in the large. In Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services (pp. 133–142). ACM. A large in-the-wild study of 100 million taps showing real-world error patterns.
- Bi, X., Li, Y., & Zhai, S. (2013). FFitts law: Modeling finger touch with Fitts' law. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 1363–1372). ACM. Quantifies how finger error dominates as targets shrink.
- World Wide Web Consortium. (2023). Web Content Accessibility Guidelines (WCAG) 2.2 (W3C Recommendation). Contains SC 2.5.8 (24×24 CSS px minimum) and 2.5.5 (44×44), the accessibility thresholds.