Cities worldwide have declared aspirations to become “10, 15, or 20-minute cities.” This goal is often part of a strategy to reduce emissions and achieve sustainable and healthy urban design by encouraging walking and cycling. The 10, 15, or 20-minute city or neighbourhood — which, for generality, we refer to as the x-minute city — is a type of design aimed at reducing car dependence by enabling urban residents to walk or cycle to essential amenities within x minutes from their home. Due to the benefits which include sustainability, health, and social cohesion, the concept has been promoted by the international C40 Cities as part of their post-pandemic Green and Just Recovery Agenda. However, missing from the current rhetoric around these “cities of proximity” is clear guidance on evaluating progress towards this goal. In this paper, we contrast measurement approaches and discuss important considerations for planners adopting the x-minute city goal. To do this, we measure the proximity of the 500 largest cities in the USA and 43 urban areas of New Zealand. We also present an interactive tool to visualise and explore proximity within the urban areas.