=COUNTA(value1, value2,...value30).
The arguments (e.g. value1) can be cell references, or values typed
into the formula. The following example uses one argument -- a reference
to cells A1:A5.
Note: COUNTA will count cells with formulas — including those that look empty, because they evaluate to "", e.g. =IF(B2="","",B2). It will also count cells which had formulas that evaluated to "", but then were converted to values (Edit | Paste Special, Values). You can see apostrophes in those "non-blank" converted cells, if you add a check mark to Tools | Options, Transition tab, "Transition navigation keys."