Midpoint and Spread of a Quote

The midpoint is the average of bid and ask.

The full spread is ask minus bid.

1. 1. Midpoint

   Average the two sides.

   $$m=\frac{99.80+100.20}{2}=100$$

2. 2. Spread

   Subtract the bid from the ask.

   $$s=100.20-99.80=0.40$$

3. 3. Key idea

   Always state both numbers: the midpoint is your reference price and the spread is what you charge for immediacy.

Answer: Midpoint 100, spread 0.40