For an ISO standard size adult hand (adjust +/-13% to take into account hand size deviation from ISO standard):
For spaghetti sizes 5-6, make the ok sign with your hand, placing the fingernail of your index finger against the base of your thumb for one person, against the middle joint for 2 people, and to the tip for 3 people.
The pressure exerted by the index finger to the thumb joints should be 9.81 kPa +/- 15%.
That is an American measure. Imprecise as fuck.
The metric conversion is:
For an ISO standard size adult hand (adjust +/-13% to take into account hand size deviation from ISO standard):
For spaghetti sizes 5-6, make the ok sign with your hand, placing the fingernail of your index finger against the base of your thumb for one person, against the middle joint for 2 people, and to the tip for 3 people.
The pressure exerted by the index finger to the thumb joints should be 9.81 kPa +/- 15%.