Manufacturer's specification: max height 92cm, max length 113cm, max thickness 32cm, max weight 11.2kg.
Please make sure you have taken off your pedals beforehand. If they are too tight, you may have to go to a bike shop and get them to do it for you. If you have never taken them off before, here is a link to a very detailed and helpful video on how to do it:
And this video of how to box up a bike might also be of help.