Just in case you find this package interesting. Except some problems 
with units conversion, it's nice:

https://github.com/sulami/literate-calc-mode.el

> This is a literate calc file.
>
> Lines without "=" are ignored.
>
> All results starting with "=>" are an overlay generated by
> literate-calc-mode. That means they are displayed in Emacs, but not
> actually in the buffer/file contents.
>
> We can calculate a value like so:
>
> = 2 + 2 => 4
>
> If there is any string on the left hand side, it becomes a bound
> variable.
>
> Pi = 3.14159 => Pi: 3.14159
>
> We can use this variable below the definiton.
>
> Tau = Pi * 2 => Tau: 6.28318
>
> Results are calculated using Emacs' own calc, so you can use formulas
> as well.
>
> = round(Pi, 2) => 3.14
>
> Later bindings shadow earlier ones:
>
> Pi = 3 => Pi: 3
>
> = Pi => 3
>
> Variable names can have spaces as well:
>
> Monthly Expenses = 500 => Monthly Expenses: 500
>
> Monthly Income = 1000 => Monthly Income: 1000
>
> Annual Savings = 12 * (Monthly Income - Monthly Expenses) => Annual Savings: 6000
>
> All values are recalculated on every update in a spreadsheet-like
> fashion.
>
> Calc also has a lot of advanced features, like arrays:
>
> Numbers = [1 2 3] => Numbers: [1, 2, 3]
>
> = 3 Numbers => [3, 6, 9]


> "Fraga, Eric"<e.fraga@ucl.ac.uk>  writes:
>
> >/> I guess that the main problem is that calc is tightly integrated with/
> >/> interactive commands. Maybe ob-calc could be extended to somehow/
> >/> indicate the commands to be executed in addition to inputting stack/
> >/> entries./
> >/>/
> >/> Not sure if there is much interest in such feature though./
> >
> >/Thinking out loud, what would be better, but I have no idea how feasible/
> >/it would be, would be to have ob-calc make use of the embedded calc/
> >/functionality and syntax, so that you could write something like this:/
> >
> >/#+begin_src calc/
> >/a := 300 m/
> >/b := 2 a =>/
> >/#+end_src/
> >
> >/which would output the result of any line with => on it./
>
> I am CCing Tom Gillespie, the maintainer of ob-calc. Maybe he has
> something to say.