Touch delta distance to be uniform, independent of the pixel density

I am trying to create a scene with touch input.

I am detecting the touch input for swipe (horizontal/vertical), by remembering the mouse position when mouse gets down, by Input.GetMouseButtonDown(0), and then calculating its distance when the mouse is up, by Input.GetMouseButtonUp(0).

My problem is that I get a smaller difference between the two vectors, while testing on a low pixel density touch device, than that, while testing on a high pixel density device, for the same amount of swipe with the finger.

I know that the mouse positions which I read, by Input.mousePosition, are in pixel coordinates, and hence the problem (for each centimetre of swipe on device, more pixels are traversed on a high pixel density device). That means, the swipes are pixel density dependent.

As a side note: The reason I am using GetMouseButton, and not GetTouch, is that I need to test this on my laptop too, with a mouse. Also, I hope if I had used GetTouch instead of GetMouseButton, I would have faced the same problem....right?

Can I work around this, so that I get a uniform distance (not necessarily in pixel coordinates) for the same amount of swipe, regardless of the pixel density of the device?

Thanks :)