Even if you get a new faucet for the bathroom sink you need to buy a drain of these sizes.
Standard sink drain size.
This size is precisely the diameter of the pipe instead of the length.
While a bathroom sink s design and overall size may vary from one model to the next the drain holes are fairly standard 1 25 inches being a general standard with widths of 1 5 inches and 1 625.
This is the measurement across the center of the drain from one side to another.
So even though there are different sizes of drains for your bathroom sink according to the international code council the standard is 1 inch.
The standard size and setting every state may have different code on plumbing and it may affect the required size of the bathroom sink pipe.