Good morning, I have just noticed that \box_resize_to_ht:Nn forces the given box into a square instead of scaling the width appropriately. The other, \box_resize_to_wd:Nn works as expected as it preserves the original aspect ratio: \documentclass{article} \usepackage{expl3} \usepackage{graphicx} \usepackage{mwe} \begin{document} \newsavebox\picbox \savebox\picbox{\includegraphics{example-image-a}} \typeout{orig. size: \the\wd\picbox\space X \the\ht\picbox} \ExplSyntaxOn \box_resize_to_ht:Nn\picbox{60pt} \ExplSyntaxOff \typeout{\string\box_resize_to_ht:Nn \the\wd\picbox\space X \the\ht\picbox} \savebox\picbox{\includegraphics{example-image-a}} \ExplSyntaxOn \box_resize_to_wd:Nn\picbox{60pt} \ExplSyntaxOff \typeout{\string\box_resize_to_wd:Nn \the\wd\picbox\space X \the\ht\picbox} \end{document} Kind regards, Alexander