The sociolinguistic context of language use contributes to individuals' linguistic knowledge. However, how it does so has yet to be fully conceptualised or quantitatively investigated within the language sciences. To meet this goal, a psychometrically sound evidence-based measure that captures important aspects of contextually influenced linguistic experience is necessary. In this paper we describe the development and validation of the Contextual and Individual Linguistic Diversity Questionnaire (CILD-Q). Exploratory factor analysis was conducted with data from 353 participants (62.9% South African, 37.1% UK, Mage = 29.3, SD = 10.09). A three-factor solution best describes the structure of the CILD-Q: Multilingualism in Context (contextual use and societal practice of multiple languages within a community), Multilingualism in Practice (direct and indirect linguistic exchanges and conversational interaction), Linguistic Diversity Promotion (societal and governmental endorsement of linguistic variation). Item scores corresponding to these three factors showed sufficient reliability ([alpha]'s > 0.80). The CILD-Q provides a novel and holistic manner to measure sociolinguistic diversity and can be used when measuring individuals' language experience within and across populations from differing sociolinguistic contexts.