AFAIK Passive HDMI cables can be up to 15m in length. Running HDMI over CAT5/6 will allow you to go up to 50m, but you need special adapters for that. Where things get tricky is the HDMI specification 1.4 and 2.0 run perfectly fine at 15m with a 1080p signal. Past 15m you MIGHT have issues running 1080p @ 60fps, but again some people have no issues and others have issues.
