Issue
Excel Formula Not Calculating, just showing the text of the formula
Solution
Select the cell that is not recalculating and, on the Home ribbon, check the number format. If the format shows Text, change it to Number.
Note
When a cell is formatted as Text, Excel makes no attempt to interpret the contents as a formula.
Links
http://www.pryor.com/blog/why-is-your-excel-formula-not-calculating/