How do you know if you have wide feet?

How do you accurately determine if you have wide feet? Is there a specific measurement or size guide to follow? What factors should one consider when selecting shoes or sandals to ensure proper fit and comfort for wide feet? Could wearing shoes that are too narrow or too tight cause long-term issues with foot health or posture? Additionally, are there any tips or tricks for finding stylish yet functional footwear options specifically designed for those with wider feet?