Sleep loss impairs many cognitive functions, ranging from simple attention to working memory. This study explores the extent to which people are aware of such impairments, their metacognitive accuracy, across different cognitive tests. Healthy participants (N = 182) were randomised to one night of total sleep deprivation or three nights of sufficient sleep. The next day they performed several cognitive tests, measuring simple attention, cognitive throughput, working memory, episodic memory and executive processing (using a Stroop task). After each test, participants rated how well they thought they performed. We operationalised metacognitive accuracy as the ability to correctly identify whether one performed above or below the median. We then used Bayesian methods to estimate the difference in this ability between the well-rested and sleep-deprived groups. The probability was 55% in the sleep-deprived group, and 59% in the rested group, suggesting some decrease in performance awareness during sleep loss. However, the probability that this difference in judgements is practically significant (i.e., exceeding 10 percentage points) is below 1%. Cognitive ability generally declines during sleep deprivation, and this was at least somewhat reflected in a decrease in how people rated their performance. The question remains whether and how people compensate for any sleep-loss induced cognitive impairments.