What is the minimum size for the water supply pipe according to IPC ??

Minimum pipe size as per IPC 1/2inch i.e. 15mm

You can find the answer in this link

https://codes.iccsafe.org/public/document/code/550/9793989

The minimum size of pipe is 1/2 inch for fixture outlet such as Laundry Sink, washbasin, shower per head  

Shall be not less than 3/4 in (19.1 mm) in dimeter

In most cases, the main pipeline from the street to your home is either 3/4 or 1 inchin diameter, supply branches use 3/4-inch-diameter pipe, and pipes for individual components are 1/2 inch. 

According to international plumbing code the pipe shall be not less than.1 mm

In my field of study, we care about the flow of water, the volume of water, the quality of water, the methods of treatment of water, water, pressure and water behavior So I apologize for the answer

minimum 1/2" for sanitary fixtures.

There are no such regulations for pipe size restrictions. But sizes will vary wrt to required flow and by keeping the velocity Maximum up to 1.5 to 2.5 m/s. As per engg practice 16 mm is the minimum pipe size with used for the individual fixtures. Hope this feedback will help you guys to understand.

The minimum of supply water in plumber is 20mm

as per requried ment minimum 3/4 inches