In the UK, all-purpose flour is equivalent to plain flour. Plain flour contains no raising agents and is the most versatile flour used for all types of baked goods, such as bread, biscuits, pizza, cookies, muffins, etc. It is also used to thicken gravies and sauces. All-purpose flour is created by a milling process that mixes a combination of hard and soft wheat. By law, in the United Kingdom, additional nutrients are then added so that the flour contains a core level of nutrition, including calcium, iron, and the B vitamins niacin and thiamine. Flour also contains between 9% - 14% of protein. When a recipe calls for all-purpose flour in the US, it is equivalent to plain flour in the UK.