The Strike Water calculator, located under the Mash Calculator tab, helps you hit the temperature of your first mash step.
This calculator is approximate. After initial strike and stir, if the temperature is +/- (2 °F) / (1 °C) leave it. Otherwise mix in cool or boiling water to compensate. Use the Infuse or Add Boiling tab to track how much was added. If the temp is only slightly over, leave the mash tun lid open for a couple minutes and it will cool down by itself.
If this is new equipment or your first time mashing with this calculator, expect some variation. It should get at least within 7 °F / 3.5 °C, if not closer, after adjusting the heat loss setting. Please see the FAQ for more details:
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. Adjust the Mash Strike Heat Loss setting in your profile as needed. Expect it to take a couple tries to dial it in.
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 calculated strike temperature, and then add grains, or you will probably overshoot.
Brewing In A Cold Area:
The equations powering this feature are geared for room temp (68 °F / 20 °C). If you are brewing in a cold area, compensate accordingly. For example, if the ambient temperature is 45 °F / 7 °C, we recommend padding by up to +10 °F / +5.5 °C. Better to overshoot a few degrees and leave the lid open vs having to add boiling water to heat it up.