According to Terzaghi, a foundation is shallow if its

Explanation:

In a shallow foundation, depth of foundation is less than or equal to its width whereas, in a deep foundation, depth of foundation is greater than its width

A shallow foundation is the one whose width is greater than depth.

i.e. \(\frac{{Depth\;of\;the\;footing}}{{Width\;of\;the\;footing}} \le 1.0\)

A deep foundation is the one whose depth is greater than the width of the footing. 

i.e. \(\frac{{Depth\;of\;the\;footing}}{{Width\;of\;the\;footing}} > 1.0\)