#677 – Why the Standard Mouse Wheel Delta is 120

For a standard Microsoft mouse, you’ll notice that the value of the MouseWheelEventArgs.Delta parameter is always either 120 when you turn the mouse wheel forward one click or -120 when you turn the mouse wheel backwards one click.  You might wonder why the value of 120 is used, rather than just 1 and -1 values.

The larger number for the mouse wheel delta is used for a typical mouse so that other manufacturers of mouse devices can include a mouse wheel with more precision, which could then return a smaller value for each delta.  For example, there might be twice as many click detents on a device, which could then return a delta value of 60.

The value of 120 can be evenly divided by 2, 3, 4 or 5.  This gives a mouse manufacturer more options in dividing up the current coarser clicks into an even number of higher resolution clicks.

About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

One Response to #677 – Why the Standard Mouse Wheel Delta is 120

  1. Pingback: Dew Drop – October 26, 2012 (#1,430) | Alvin Ashcraft's Morning Dew

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