The purpose of this study is to compare perceived room dimensions - made from reclining versus standing postures - to actual room dimensions. The perceptions of subjects are reported for survey in a full-scale room with adjustable wall and ceiling-surfaces. The combinations of the three different ceiling heights and the three different (square) floor areas were presented randomly. The Method of Comparative Judgment was used; each subject was asked to estimate room dimensions using either the Method of Adjustment or Magnitude Estimation. It is concluded that: 1. From either posture, perceived ceiling height corresponds more closely to the actual as floor area increases; however, the more accurate judgments are made from reclining postures; 2. Room depth was perceived more accurately from standing postures; 3. From either posture, room volume was perceived to be larger when ceiling height was perceived to be higher or the room depth was perceived as smaller; 4. Room volume was perceived more accurately from reclining postures.