Calculate time to find block

I am looking to see how to calculate time to find a block and I think I am doing it gravely wrong. Two miners website says to divide the network difficulty by the network cash rate but this number comes out as a very small decimal.

Difficulty 102k

Network hashtate ~7Th

102,000 / 7,000,000,000,000 = 1.45714286E−8

Does anyone know what am I doing wrong and what is the unit of time the answer comes out in?