I'd like to build a desk from a sheet of wood and four metal legs at each corner. Appearance is not critical; a rugged built-from-scratch look is quite fine. Dimensions will be 1200mm x 650mm (47" x 26").
If I build this from plywood, how can I calculate how thick the plywood must be to avoid the desk bending in the middle?
In a perfect world, the desk is super strong - enough that I could sit in the middle (at 75kg/165lb). In a realistic world, it needs to hold two large monitors and various computer accessories, totalling no more than 20kg/45lb.
I've found a place that offers hardwood plywood at 15mm (0.6"), 18mm (0.7") and 25mm (1") thickness. How do I determine which thickness is sufficient for my plans?
I've assumed hardwood plywood is a reasonable choice, but softwood plywood would be 25% cheaper if I can get away with it.