Calculate Sum Automatically

1. Select the cell immediately below the column of values to be summed.
2. Press Alt + = (Alt and 'Equal to' sign)
3. Excel will automatically write the Sum function and select the numeric range
4. Hit Enter!

Understand how to format your Excel sheet in few easy steps: http://learnexceleasily.blogspot.in//2013/11/quick-formatting-and-beautification.html