Calculating variance from multiple columns from the same table

P_P2595 , Unpivot the all column other than Id and description , then you can have measures like

M1 = calculate(Average(Table[Value]), filter(Table, Table[Description] ="Start") )

M2= calculate(Average(Table[Value]), filter(Table, Table[Description] ="End") )

Diff = [M1] -[M2]

Learn Power BI: Power Query UnPivot Data, Pivot Data, Transpose Data, Query Fill Up, Fill Down: https://www.youtube.com/watch?v=cN8AO3_vmlY&t=36407s

Unpivot Data(Power Query): https://youtu.be/2HjkBtxSM0g

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.
https://1drv.ms/u/s!AiUZ0Ws7G26RiGy6Yf6quAn_ATjG?e=zsB0R6

Hi,

Please find attached my solution file.

Hope this helps.