Does this answer your question?

#+NAME: tt
| num | ID |
|-----+----|
|   1 | A  |
|   2 | B  |
|   3 | C  |
|   4 |    |
|   5 | E  |

#+BEGIN_SRC emacs-lisp :var tt=tt
(length tt)
#+END_SRC

#+RESULTS:
: 5

Best wishes,
    Neil


On Wed, 18 Sep 2019 at 18:39, Nathan Neff <nathan.neff@gmail.com> wrote:

> Hello all,
>
> I have a table like this:
>
>
> | ID |
> |----|
> |  2 |
> |  3 |
>
> and I want to know how many rows there are w/o the ID heading
> and w/o the horizontal separator.  I found the
> org-table-toggle-coordinate-overlays
> which displays an overlay showing the row number:
>
> https://www.evernote.com/l/AOJvD5ty6RRIBYAcSWV-047CKCHT5NIAhl8
>
> However, the heading is included in the row number (which makes sense).
>
> Is there a way to ignore lines above a heading (or mark a heading in some
> way?
>
> I found a way to add a seq. number by using Calc [1] but I was wondering if
> there's a way to tell the org-table-toggle-coordinate-overlays not to
> count the
> heading.
>
> Thanks,
> --Nate
>
> [1]
>
>
> | num | ID |
> |-----+----|
> |   1 | A  |
> |   2 | B  |
> |   3 | C  |
> |   4 |    |
> |   5 | E  |
> #+TBLFM: $1=vlen(@I..0)
>
>
> https://stackoverflow.com/questions/9267050/how-to-achieve-a-row-index-column-in-emacs-org-mode-using-a-calc-column-rule
>
>
>