The antonyms for the word "mis-calculating" would be "calculating correctly," "calculating accurately," or "calculating precisely." These antonyms suggest that the person or entity performing calculations has performed their task with the appropriate care and attention, leading to an outcome that is correct and reliable. By contrast, the word "mis-calculating" implies that errors were made in the calculation process, resulting in an incorrect or unreliable outcome. It is important to strive for accuracy and precision in calculations, especially in fields such as finance, engineering, and science where small errors can have significant consequences.