That max age formula is pointless and contradicts the minimum age formula. For 29 the min age based on the min age equation is 21.5 which I’d say can be rounded up to 22, which sounds more reasonable than a 29 year old dating an 18 year old, which isn’t illegal sure, but I’m sure plenty of people would be raising an eyebrow at it.

That max age equation would mean that a max age for 14 would be 21. In contrast the min age for a 21 year old is 17.5, which can be rounded up to 18. Yymv on that one in particular, but I’m sure we can all agree that a 21 year old dating an 18 year old is a lot less sus than them dating a 14 year old. The minimum age formula seems fine enough on its own, not necessarily a universal rule but enough of a guideline to go by. If you want to calculate based on the younger age, just re-arrange the formula. With the older age being AgeO and the younger age being ageY, you go from ageY = (AgeO/2) + 7 to AgeO = (ageY - 7)*2.