Answer: 56 inches Explanation: Between 4" and 6" depending on the garage. 
Cronin Construction & Resource Management, LLC 
Answer: 45 inches Explanation: Industry standard for residential garage floor thickness is 45" with a thickened edge where load transfer occurs. 
Maven Group LLC 
Answer: 45 inches Explanation: Its the average standard for strength and durability of concrete for its purpose to accomidate average vehicles. 
BAT Concrete llc 

ProMatcher 
Answer: 67 inches Explanation: The standard concrete garage floor is six inches thick and, with use of proper control joints, should be thick enough to withstand normal use. 
Colorado Concrete 
Answer: 45 inches Explanation: Garage floors are 35 inches 
Design4 
Answer: 45 inches Explanation: If placed proper on compacted material with reinforced concrete 4 to 5 inches is good. 
Concrete services 

ProMatcher 
Answer: 56 inches Explanation: A 6" slab is required for parking vehicles 
BellPro Construction LLC 
Answer: 56 inches Explanation: We use 5"to6" thick concrete if there will be heavy trucks driving on it. 
A to Z Fence and Concrete 
Answer: 45 inches Explanation: 4 is sufficient if done correctly with 8 in perimeter 
DIRTCO CONSTRUCTION 

ProMatcher 
Answer: 56 inches Explanation: to support weight of automobile floor should be 6" and reinforced 
LPG,LLC 
Answer: 45 inches Explanation: The standard is 45 inches with 4000 psi concrete with steel mesh or fiber 
h and h company 
Answer: 34 inches Explanation: Residential concrete garage slabs are typically 4" 
Concrete & Beauty Design 

ProMatcher 