How to auto resize panes in tmux?

I suggest resizing multiple panes with one of the five tmux presets:

C-b M-1             # vertical split, all panes same width
C-b M-2             # horizontal split, all panes same height
C-b M-3             # horizontal split, main pane on top,
                      other panes on bottom, vertically split, all same width
C-b M-4             # vertical split, main pane left,
                      other panes right, horizontally split, all same height
C-b M-5             # tile, new panes on bottom, same height before same width

M denotes the meta key, usually bound to ALT.

On Macs the meta key is usually Esc, as mentioned in the comment below.

See the tmux manpage for more information.

PREFIX Space is shortcut for :next-layout