# How to Calculate the First Moment of Area

In structural engineering applications, the first moment of area is a calculation that is used to determine shear stress distributions. It is a relatively simple concept which involves the moment of a surface around an axis.

$Q_y = x_c A\newline\newline Q_x = y_c A$
Where:

Qx = first moment around the x axis (ft3 or m3)
Qy = first moment around the y axis (ft3 or m3)
xc = distance to centroid from the x axis (ft or m)

yc = distance to centroid from the y axis (ft or m)
A = Area (ft2 or m2)

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