To find the area of a rectangle, you can use the formula:
\[ \text{Area} = \text{length} \times \text{width} \]
In this case, Hiram's blanket has a length of 55 inches and a width of 43 inches. Therefore, the expression he can use to find the area of the blanket is:
\[ 55 \times 43 \]
So, the expression to calculate the area is \(55 \times 43\).