How do they determine how much my weekly workers’ comp checks are for?

It is simple math.  They take your average weekly wage, which is the average of your gross (before tax) income for the 13 weeks prior to your accident.  But you don’t get paid this amount. The law only requires the insurance company to pay 2/3 of that amount. For example, if your average weekly wage is $600 then you would receive $400 as your weekly workers’ compensation benefit if you are entitled to it.