How to find number of rows in cursor

The cursor_variable.%ROWCOUNT is the solution. But its value will be 0 if you check it after opening. You need to loop through all the records, to get the total row count. Example below:

DECLARE 
  cur sys_refcursor;
  cur_rec YOUR_TABLE%rowtype;
BEGIN
  OPEN cur FOR
  SELECT * FROM YOUR_TABLE;

  dbms_output.put_line(cur%rowcount);--returning 0

  LOOP
    FETCH cur INTO cur_rec;  
    EXIT WHEN cur%notfound;
    dbms_output.put_line(cur%rowcount);--will return row number beginning with 1
    dbms_output.put_line(cur_rec.SOME_COLUMN);
  END LOOP;

  dbms_output.put_line('Total Rows: ' || cur%rowcount);--here you will get total row count
END;
/

You must open the cursor and then fetch and count every row. Nothing else will work.