Formulate lets you use Excell - like formula syntax in html tables. To make a calculation, just use =A1+B2+B3/B4 or similar formula in any cell of your table.
You can now use for example SUM(A1:G34) formula to calculate the sum of cells or AVG(A1:G34) to calculate avarage value.
If you want to see how it works - See some examples and tests!
Formulate is running as a service and connected to Evernote. When you edit any note with Formulate tag, the note gets recalculated with formulate. All for free!
#More formulas If you want more formulas, fork me on github!