In general, cats and dogs can be safely spayed / neutered when they reach 12 weeks of age and weigh a minimum of 3 pounds. Check with your pet's full-service veterinarian to see what their actual requirements may be.
Source: The Optimal Age for Spay / Neuter: A Critical Analysis of Spay Neuter Literature, Philip A. Bushby DVM, Mississippi State University, MS, USA
& The MBM Focus published by the Margaret B. Mitchell Spay / Neuter Clinic, Spring / Summer 2021 Edition
No, your pet isn't broken. Still, when is the best time to have your pet "fixed"? This is one of the most common questions posed to veterinarians by pet owners. Research has proven that early spay / neuter has multiple health, behavioral and community benefits. Recommendations can be made based on species, size and life situation. However, the decision to spay or neuter or not is a good conversation to have with your pet's full-service veterinarian.
Shelter dogs and cats: Prior to adoption (as young as 6 weeks of age)
If the animal is too young to be spayed or neutered when adopted, the adopter usually pays a spay / neuter deposit that is refunded when proof of surgery is provided to the shelter
Cat (male or female): Prior to 5 months of age
Dog (large breed female): Prior to 5 months of age
Dog (large breed male - free roaming): Prior to 5 months of age
Dog (large breed male - house pet): After growth stops - 15 to 18 months of age
Recommended Age to Spay / Neuter: