Converting acceleration with gravity to pure acceleration?

Using event.accelerationIncludingGravityon Android, it returns a value

x: -0.2
y: +0.1
z: +9.1

when resting on a flat surface. However, I want to get acceleration without gravity, but event.accelerationnot supported. Is there a way to convert it to math? In HTML5Rocks is an example of removing the factor of gravity, but it does not seem to work.

  // Convert the value from acceleration to degrees acceleration.x|y is the 
  // acceleration according to gravity, we'll assume we're on Earth and divide 
  // by 9.81 (earth gravity) to get a percentage value, and then multiply that 
  // by 90 to convert to degrees.                                
  var tiltLR = Math.round(((acceleration.x) / 9.81) * -90);
  var tiltFB = Math.round(((acceleration.y + 9.81) / 9.81) * 90 * facingUp);

Sample script acceleration of graphic display (not from HTML5Rocks)