You can go one of two ways, ingredients x4 or total cost x3, both of these will give you an good basis. The beauty of this is that it allows for ingredients and costs to scale as you either change to more, or less, costly ingredients, or scale in volume.
I have found that unless you are meticulous and work alone, 2x does not account effectively for overhead, almost all industry studies will agree with that. I do not compare to surrounding restaurants, for two reasons, I don't know how well they are doing, and I don't know their food costs and margins. This holds true for what I do now, I never charge based upon what others charge, I charge what I am worth.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."