Rationalize

Rationalize[x] converts an approximate number x to a nearby rational with small denominator.

Rationalize[x, dx] yields the rational number with smallest denominator that lies within dx of x.

Examples

Convert to rational:

Rationalize[0.333333]
(* 1/3 *)

With tolerance:

Rationalize[3.14159, 0.001]
(* 22/7 *)

Please visit the official Wolfram Language Reference for more details.