Length of the usable portion of a white piano key

[nauru]

Hi I was just wondering what is the standard length of a white piano key?  I am referring to the portion of the key which is visible externally, and usable while playing.  I'm not talking about how far inside the piano body it extends. 

Is there a standard length for the playable portion of white keys?  Is the length different between upright and grand pianos?  What about between manufacturers?

Thanks! 

[keys60]

There is no standard lenght for the keys. They vary slightly between manufacturers. Roughly 6 inches on uprights, a little longer on grands give or take a fraction here or there.