Mass-Energy Conversion Feats

When is it used?
Matter-energy conversion, the equation E = (mass)(speed of light^2) should only be used in a calculation if the feat clearly states that this is the method used for it. As for the reasons?
 * Utilizing the mass-energy conversion formula to calculate objects from nothing produces a result that is always drastically higher in comparison to what is intended to be portrayed on screen.
 * This means that characters who are able to perform feats like this almost never have the feats equivalent to the theoretical energy that would be required for the creation of that object.
 * Most of the time in fiction, due to the laws of real-life physics being ignored in one way or another, the assumption that the object was created from scratch following the process of mass-energy conversion is rarely justified, and there could be some other application of fictional science (or plot) that may in play.
 * The creation of matter from nothing, such as the creation of objects out of nowhere, the ability to increase the size & mass of an object, as well as beings of energy taking physical form & regeneration of injuries (when nothing was there previously) is not something that could be properly explained by real life science.
 * In order to create something, you always need some other material to create that "something" from, including the molecules & atoms that make up that object (or parts of that object that forms the whole). Thus, any process of creation that ignores this is directly violating the laws of physics, and is closer to reality warping.

Work in progress