The feet are 20 inches apart side to side, and 8 1/4" front to back. So they form a 20"x8 1/4" square. The feet themselves are 5/8" diameter.
But, if they don't align with your stand, you can always get some stick-on rubber feet and put them where you need.
EDIT: Adding metric measurements: 50.8cm x 21cm, feet are 1.6 cm diameter.