How much maximum length allowed for a UTP cable?

the maximum allowed length of a Cat6 cable is 100 meters (328 ft). This consists of 90 meters (295 ft) of solid "horizontal" cabling between the patch panel and the wall jack, plus10 meters (33 ft) of stranded patch cable between each jack and the attached device.

It depends on the application that you are using the cable in. If you are using it in Networking and broadcasting like CCTV , then it should n't exceed100 m. If your distance is greater than100 m , then you could use extenders , repeaters or switches. Some extenders are active , others are passive. Some active extenders could give you a distance of1000 m.

The maximum length for a cable segment is 100 m per TIA/EIA568-5-A. If longer runs are required, the use of active hardware such as a repeater or switch is necessary. The specifications for 10BASE-T networking specify a100-meter length between active devices. This allows for90 meters of solid-core permanent wiring, two connectors and two stranded patch cables of5 meters, one at each end.

Maximum is100 metres, But it is not recommended to use more than80 metres

As per structured cabling procedures -90 meters

If you're probably talking about Ethernet, and the maximum end-to-end cable length in Ethernet (at least for100Base-TX,1000Base-T and10GBase-T) is100M

Depends on quality of wire you are using. If you have good quality of wire and CAT-6 then there should not be a problem carrying data up to120 Mtr. 

Depend on your solution1 gig or10 gig?.

1 Gigabyte Network.

if1 gig the maximum allowed length of a Cat6 cable is 90 meters (295 ft). This consists of 80 meters (262 ft) of solid "horizontal" cabling between the patch panel and the wall jack, plus7 meters (22 ft) of stranded patch cable between each jack and the attached device.plus2 -3 meters (6 -9 ft) of stranded patch cable between each patch panel jack to the attached switch.

10 Gig Network Cat6 A

just consider instead of90 mtrs to70 mtrs only.

The Maximum length allowed for90 meters

a maximum distance of100m between to host then u can add a switch

100meter in case of switching,while in POE case it vary