How many judges you need is entirely dependent on the size of your competition, but our heat scheduler helps you conceptualize this - and you can even manage your judge registrations and lane assignments using the heat scheduler.
In general, the minimum number of judges you'll need is dependent on the maximum number of athletes you'll have competing at any one time.
If you have only one workout running at a time, you'll need a minimum of one judge per lane. If all your workouts will have 10 lanes running at a time, then your minimum judge count will be 10.
If you have multiple heats competing on different stages at one time, then you'll need at least one judge per each lane that is concurrently taking place. For example, if two workouts each housing 10 lanes are occurring at once, then your minimum judge count will be 20.
Factor in rotating schedules and drop-outs, and you may need 150-200% more judges than what you actually need at your highest capacity.
In the first example, that would mean 15-20 judges slated is ideal. In the second, 30-40.
If you don't have the capacity to have that quantity of dedicated judges, it is helpful to have a contingent of "floater" volunteers that you could tap in to judge if needed. And you can have them all register (and plugged into the heat scheduler) using the Strongest platform.