The number of noodles in pasta refers to the classification of pasta. Generally speaking, for the same brand of pasta, the larger the size, the larger the outer diameter. Pasta sizes from small to large are the sizes of pasta from thin to thick. Generally speaking, those smaller than size 5 are thin pasta, and those larger than size 5 are thick pasta or other shapes. So the difference between No. 3 and No. 5 pasta is the thickness. No. 5 pasta is thicker than No. 3 pasta.