my-split-window.el

(require 'cl-lib)

(cl-defun split-window-vertically-n (&optional (num_wins 1))
  (interactive "p")
  (cond ((<= num_wins 2)
         (split-window-below))
        (t
         (split-window-below
          (- (window-height) (/ (window-height) num_wins)))
         (split-window-vertically-n (- num_wins 1)))))

(cl-defun split-window-horizontally-n (&optional (num_wins 1))
  (interactive "p")
  (cond ((<= num_wins 2)
         (split-window-right))
        (t
         (split-window-right
          (- (window-width) (/ (window-width) num_wins)))
         (split-window-horizontally-n (- num_wins 1)))))