A map of reach
People use phones one-handed while walking, holding a rail or carrying coffee (Karlson et al., 2008). The thumb sweeps an arc over the lower screen near the palm, while the opposite top corner needs a regrip. Bergstrom-Lehtovirta and Oulasvirta (2014) modelled this functional area from hand size, grip position and screen size, so the zone varies by person and device.
Size and location interact
Parhi, Karlson and Bederson (2006) found errors rise sharply below a certain target size for thumb use, and Park and Han (2010) showed performance also depends on screen location. In hard-to-reach spots the stretched thumb errs more than Fitts's law alone predicts. Two-handed use is more accurate (Wobbrock et al., 2008), but people switch constantly, so key actions belong low and central while destructive ones go out of easy reach.
Principles and limits
The thumb zone explains patterns like bottom navigation, bottom sheets and floating buttons (Hoober & Berkman, 2011). Left-handers, tablets, landscape mode and foldables shift the zone, so symmetric or centred layouts are safer. Packing everything into easy reach also invites accidental deletes or payments, so pair it with undo and confirmation. It is most useful alongside touch target size.
FAQ
- What is the thumb zone in simple terms?
- It is the area of the screen your thumb reaches easily when holding the phone in one hand; frequent buttons should live there.
- Do left-handers share the same map?
- No, it mirrors, so bottom-centre positions that suit both hands are safest.
Sources reviewed: 2026-10-27
References
- Bergstrom-Lehtovirta, J., & Oulasvirta, A. (2014). Modeling the functional area of the thumb on mobile touchscreen surfaces. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 1991–2000). ACM. Models the reachable thumb area from hand size, grip and device size; the basis for thumb-zone maps.
- 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. A classic experiment on target sizes for one-handed thumb use.
- 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 how both key size and screen location affect thumb performance.
- Karlson, A. K., Bederson, B. B., & Contreras-Vidal, J. L. (2008). Understanding one-handed use of mobile devices. In J. Lumsden (Ed.), Handbook of research on user interface design and evaluation for mobile technology (pp. 86–101). IGI Global. Explains when and why people use phones one-handed.
- Wobbrock, J. O., Myers, B. A., & Aung, H. H. (2008). The performance of hand postures in front- and back-of-device interaction for mobile computing. International Journal of Human-Computer Studies, 66(12), 857–875. Compares hand postures, clarifying one- versus two-handed performance.
- Hoober, S., & Berkman, E. (2011). Designing mobile interfaces. O'Reilly Media. A practical pattern library for choosing bottom placement and navigation 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. Models finger accuracy, explaining larger errors in hard-to-reach areas.