Does anyone know the formula for calculating the force or torque needed when a grader blade rotates so I can properly size the rotary hydraulic motor?

[Lucciano M.]

I'm trying to size a rotary hydraulic motor for a grader blade turning system and need the proper formula for calculating the required torque under load. Most examples online are too general. Does anyone know the correct calculation or have a simple real-world example for grader blade rotation?