Yep. There are general equations out there for relative creatine needs. It's not perfect because you can have very small individuals that have nutrient needs in excess of what you'd expect and very large individuals with smaller nutrient needs than you'd expect. Useful from a practicality standpoint though. I've seen 0.3 g/kg for the loading phase and 0.03 g/kg for maintenance dosing. When I've plugged in bodyweight (in non-obese individuals) or ideal body weight (in obese individuals) it works pretty well and comes out to ~20-25g and ~3-5 g respectively in most cases. Below is a good paper on this
Creatine supplementation with specific view to exercise/sports performance: an update