Personal travelling unfavourably contributes to the emissions of greenhouse gases, which adversely causes long-term damage to the climate. In order to reduce the associated negative impacts of such activities on the environment, there is a wide consensus that enhancements and innovations in the efficiency of vehicles will not be enough, but behavioural changes are needed. For this, individuals should be able to measure their travel-related carbon emissions, and such emissions could be determined by using personal carbon footprint calculators, which proliferated during the previous decade. However, various research questions related to such calculators are yet to be answered in published literature. As such, this paper investigates how key transport-based calculators account for emissions from personal transport-related activities following a top-down analysis. In this endeavour, ten such calculators are investigated through a set of formulated research questions to analyse their scope, calculation approach used, transparency, consistency of results, communication methods utilized and platform differences. Results revealed that the calculators have varying granularity, have limited transparency, provide significantly inconsistent results in some cases and are not fully engaging end users. Based on limitations identified, recommendations have been proposed through a taxonomy to guide policy-makers towards improving such tools.