How To: Disassemble and Return Your Aeron Classic Office Chair 

Would have been really useful if they’d said this

Since he put the back rest horizontally, I measured the height of it and added ~2 inches for clearance. Then I measured the height of the lowered seat and armrests and added a few inches again. It's about 26" wide/deep and 24" tall for my chair, but I reckon it'll vary by the size you have.

26x26x26”

Thank you for your comment and suggestion!

www.crandalloffice.com/shop/chairs/herman-miller/aeron/refurbished-herman-miller-aeron-chair-carbon-black-frame/

You should be less rude. This video is useful to pack the chair. Removing the base messes up with the hydraulic system.