I wanted to know what the luggage allowance is? I'm going on air China.

I found the following free allowance information on their website. You should pay for the extra piece, kilos, and volumes.
Free allowance of checked baggage (dimension should be smaller than 158cm):
First-class and business cabins:
2pieces at most, each weighs less than 32 kg.
Economy cabin:
2 pieces at most, each weighs less than 23kg.

Free allowance of carried baggage (dimension should be smaller than 115cm):
First-class and business cabins:
2 pieces at most, each weighs less than 8kg
Economy cabin:
1 piece, each weighs less than 5kg.