Piecewise[{{x/12.92, x<=0.04045 & x>=0},{((x+0.055)/1.055)^2.4, x>0.04045 & x<=1}}]

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.