The cake is measured in inches, 1 inch =2.52 cm, so the diameter of a 20-inch cake is about 50 cm. A cake of this size is suitable for 25-30 people.
Cake size comparison table
3, 10 inches (in), diameter is about 25 centimeters, 3 pounds, suitable for 5-8 people,
4, 12 (in) inches, diameter is about 30 centimeters, 4 pounds, suitable for 8-12 people.
7, 18 (in) inches, about 45 centimeters in diameter, 7 pounds, suitable for 20-25 people.
8, 20 (in) inches, about 50 centimeters in diameter, 8 pounds, suitable for 25-30 people.