How much is half a degree in Fahrenheit?

0.5 deg F = - 17.5 deg Celsius

But each half degree F is equal to 0.277... deg C. This apparent distinction is because neither the F scale nor the C scale is an absolute scale.

What a half a degree represents.

The Fahrenheit scale was set up so that 0oF was the temperature that sea water froze at. This assumed that sea water was consistent throughout the world. The boiling point of fresh water was set at 212oF. These two boundaries established the freezing point of normal water at 32oF. A degree Fahrenheit would be 1/180 of the temperature between freezing and boiling. Half a degree would be 1/2 of 1/180 or

1/360th of that amount.

The metric system is based on the freezing and boiling points of water but divided the temperature increase into 100 equal parts