{calculations} is about calculations in (La)TeX documents. A popular package is calc, although others also exist (fp, pgf, and LaTeX3 packages, e.g xfp).
calculations is about calculations in (La)TeX documents. A popular package is calc that redefines most length- and counter-setting macros (like \setcounter, \addtocounter, \setlength and \addtolength) to allow expression-style input.
Regular mathematical calculations are possible via the fp package, which provides infix or RPN notation for calculations. The powerful pgf package provides a similar and more extended functionality, as does LaTeX3's l3fp.
Please note that the features of l3fp can be used outside of LaTeX3 code with \fpeval by loading the xfp package.
