How is general liability insurance calculated for a general contractor in NY?

Well it depends on the company providing the policy. Most will calculate the premium based on your direct payroll and they could also add in payroll for your subcontractors. If you don't want to pick up the premium charge for your subcontractors you will have to show the insurance company that the subs carry their own liability insurance policy. Hope this helps. By the way NY is a difficult state to even find reasonable liability insurance for general contractors.