The antonyms for "calculated roughly" can vary depending on the context in which the phrase is used. If the phrase is referring to an estimate or approximation, then antonyms could include "exact," "precise," "accurate," "meticulous," or "detailed." On the other hand, if the phrase refers to a lack of care or attention to detail, potential antonyms could include "careless," "haphazard," "imprecise," "inaccurate," or "reckless." In general, the opposite of "calculated roughly" suggests a deliberate and thorough approach to a task, project, or problem, rather than a careless or slapdash one.