Although reduced sleep often underlies traffic and occupational accidents, convenient sleepiness testing is lacking. We show that posturographic balance testing addresses this issue, because balance testing predicts hours of wakefulness, which could facilitate sleepiness testing. Here, we equate balance scores from separate trials, blinded to the experimenter, with those recorded as a function of known and increasing time awake (i.e. during sustained wakefulness); we show, that the time awake in separate trials is posturographically measurable: positive predictive value 69%, sensitivity 56%, and specificity 96%. These results encourage further work developing posturographic sleepiness monitoring.