Guesstimations are unofficial and approximate calculations made without any concrete data. Synonyms for guesstimations include estimates, approximations, conjectures, and speculations. These words imply that the calculations are based on limited information and may not be entirely accurate. Another synonym for guesstimations is rough calculations, which means that the figures are done quickly without careful consideration or analysis. Other terms for guesstimations include educated guesses and ballparks. All these words indicate that there is a degree of uncertainty in the calculations, and they should not be taken as definitive or reliable.