[rootusrootus]

I wonder how well the "pixel distance scrolled" translates into the actual distance your finger moved the wheel.

[lukax]

This is a bit hard to calculate because of scroll acceleration and inertial scrolling.

[azhenley]

My Logitech MX mouse's wheel keeps spinning and spinning, so not well at all.

[eqvinox]

You'd also need to identify the size of the scroll wheel, which is particularly hard if the user has multiple input devices and you don't even know which one they used :)

(e.g. touchpad + mouse)

[jagged-chisel]

Some system-level code would be ideal here. I wonder if, say, Apple logs this info locally (iPhone, iPad, Mac) for touching the screen, the trackpad, or moving a mouse across a surface.

[mamon]

My rough estimate is: 2cm finger movement per 800px scrolled.

[phoenixdblack]

Or scrolled through swiping on the phone. I think this would be pretty difficult considering the different pixel densities on touch devices.