All my recipes are using the metric system. As it is the best and most useful way of measuring things*. I also use Celsius, as I think it is normal to see water become ice at 0 and start boiling at 100. 🙂
So anybody have to convert themselves to anything they are comfortable with.
*My belief comes mainly from what I am myself used to. But also expiring the difficulty that Americans have to know their own gallon, quarts and ounces. And once meeting a New Zealand that did not know that it is a difference between US ounces and Imperial ounces.