How come people keep asking the same questions without even trying to do a search.

I'm sure this has been discussed in the past quite several times.

Anyway, as stated in QA webpage

http://www.qatarairways.com/global/en/baggage.html

Also consider that the airliner has additional restrictions based on destination , dates, and timings of the flights. Just check with the airline.

And in case you have extra weight you must go to the nearest office for details.

Regards!!