How much does a cat have to weigh to be spayed?

Weight is usually a factor when spaying or neutering. Some vets will wait until the kitten weighs more than 2kgs, or 4lbs as to limit any possible risk with the anaesthetic. Age is also a factor. Usually 4-6 months is ideal for a spay, but it can be done any time after that. Contact the vet that you plan to have do it and they will tell you the guidelines for the procedure as all vets have different requirements.