The number of units used in Botox varies widely and is based on muscle size, gender, metabolism

https://www.scribd.com/document/984154100/Botox-for-Crow-s-Feet-vs-Forehead-Lines-Which-to-Treat-First-208546

The number of units used in Botox varies widely and is based on muscle size, gender, metabolism, and desired softness of movement.