Sicyon is all-in-one freeware tool for everyone dealing with sci/eng formulae. The core of Sicyon is an expression calculator and the principal features are: estimate a function using variables, user-defined functions and over 50 built-in functions; plot/tabulate a function; find real roots, minimums, maximums and definite integral of a function; fit a function over data set; sophisticated units converter; database reader with various physical and chemical constants; various tools as add-in applications.