Americans call hash the pound sign or number sign.
In American English the symbol # commonly referred to as hash is called the number sign or pound sign.
The number sign is a common way to refer to the symbol when it's used to denote a number as in #1.
On telephones and keypads or when referring to weight the # also known as hash is called the pound sign.
When you call an automated system and it asks you to press a number and the pound sign they are saying you should press the numbers and then the # key on the phone.
2# can refer to 2 lbs of sugar or other ingredients.
Hash is a more general term that is often used in online contexts and especially when referring to the symbol that is used in hashtags.
The symbol can also be called a hash mark or crosshatch or an octothorpe.
The # symbol is well known variously in English-speaking regions as the number sign, hash, or pound sign.
The symbol # has also historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois and having been derived from the now-rare ℔.