Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. calcŭlo, āre, v. a. [calculus], to calculate, compute, reckon (late Lat.).
2. calcŭlo, ōnis, m. [1. calculo], a computer, accountant, Aug. Ord. 2, 12; Anthol. Lat. II. p. 268, 1.