Formal verification techniques enable the detection of complex quality issues within system specifications. However, the majority of system requirements are usually specified in natural language (NL). Manual formalisation of NL requirements is an error prone and labor intensive process requiring strong mathematical expertise and can be infeasible for large number of requirements. Existing automatic formalisation techniques usually support heavily constrained natural language relying on requirement boilerplates or templates. In this paper, we introduce ARF: An Automatic Requirements Formalisation Tool. ARF can automatically transform natural language requirements into temporal logic based formal notations. This is achieved through two steps: 1) extraction of key requirement attributes into an intermediate representation (we call it RCM), and 2) transformation rules that convert requirements in RCM format into formal notations.