Household kitchen faucet size: We often hear people talk about the specifications of the faucet, and often say that the score is 1/2, 3/4, etc. 1/2, 3/4 is English system, converted into metric system: 25.4mm= 1 inch. Divide 1' into 8 parts according to one inch: 1 minute is pipe diameter 1/8*25.4mm=6, etc.