holding a mobile hone to use an app

Consider Thumb Preference in Mobile Phone User Flows

The introduction of intuitive user flow mapping has been one of the best things that ever happened to mobile phone apps. Granted, it’s fantastic for any software and web development in order to predict user pathing and smooth their experience. However, in the mobile realm, few things matter more than an excellent and easy user flow. Especially when you consider that users are often limited to the use of a single thumb.

Mobile Phone App User Flow and the Thumbs

When mapping out the set of screens, it’s easy to forget that mobile users are navigating without a mouse and keyboard. When we hold a phone, it’s with the fingers cradling the back of the phone and the thumbs doing all the work. Sometimes, we hold the device in one hand and poke at it with the other.

This means that your user flow for mobile phone apps and phone-sized resolutions should be designed with thumbs in mind. Thumbs move from point to point hinged on a lever off to the side of the screen. Each thumb favors buttons on its own side of the screen and it the thumb tip prefers to sweep in a varied semi-circle over the screen.

One-Handed Mobile Phone Use

Then there’s the consideration that so many of us use our phones, not landscape and two-handed like a blackberry but one-handed propped up in a single palm. And you know what that means, tapping out with a single one-sided thumb. When using a phone one-handed, users generally favor one side of the screen over the other.

Buttons on the right-hand side of the screen are therefore easier to tap because they require less reach for the right-handed majority. In fact, some apps spread their buttons out so far that it is difficult for a user following a single user flow to complete a task without adjusting their grip on the mobile phone to extend their thumb.

Larger Screens – Longer Reach

Speaking of extension, larger phones also complicate this problem as they add physical distance between a thumb and a screen. In your aspect ratio designs, you should consider that larger screens actually need more thumb-friendly designs.

Semi-Circle Intuition

Next, consider the movement of the thumb. It can extend in length and tap-point but also has a natural arc of movement.

A UI design that considers one-handed and mobile thumb navigation might begin showing a preference to semi-circle controls from the assumed location of a user’s thumb base rather than the purely rectangular designs we inherited from the 90s era website design. Remember that the hand is organic. Therefore mobile UI design should be organic, too.

Right or Left Handed

Of course, not every user is going to be right-handed. About 10% of the population is left-handed, and a larger number use their phones with their off-hand when it’s more convenient. This means that your mobile phone apps may also want to keep handedness in mind, especially when creating thumb-centric user flows.

The easiest way to deal with this is a simple toggle in the menu that will switch your thumb-centric controls. In fact, for real versatility, you can add a two-thumbs design into the mix as well if you have the time, budget, and inclination.


Creating an intuitive UX through the UI design is all about understanding how customers will be using your app. Not just the tasks they want to complete, but how their hands interact with the mobile phone. Indeed, it matters how they are pushing each button built into the user flow. For insights into UI and UX that really make a difference to the user, contact us today!