If I were to a pack a suit jacket and pants in a box what dimensions would you recommend?

How To Pack a Suit | Brooks Brothers
1. Lay suit facedown on a flat surface.
2. Fold left shoulder back.
3. Turn right shoulder inside out, then tuck left shoulder into the right.
4. Fold in half lengthwise and then fold horizontally.
5. Place folded jacket in center of outstretched trousers.
6. Fold trouser bottoms over jacket and repeat with top of trousers.
magazine.brooksbrothers.com/how-to-pack-a-suit/

Then measure what you have and get a box that size.