At this point the equation is basic, based off Palmer's equation found here. It works best for batch sparging. The limitations come from a single equation trying to model everyone's equipment (mash tun thermal properties), and varying processes.

NOTE: The strike calculator assumes your tun will absorb heat (a few degrees will be absorbed by the mash tun, this varies widely by the type of mash tun). Even if you 'pre-heat' the tun with a little boiling water, this may still be the case. Do not stabilize the tun at the strike temperature, and then add grains, or you will overshoot.