This study describes the ability of young adults (N = 177, 75% female) aged 16-26 years to estimate the size and calories in typical portions of common foods. Participants served themselves typical portion sizes of 8 foods at breakfast (n = 63) or 6 foods at lunch or dinner (n = 114). Portion size selections were unobtrusively weighed and converted to volume measures. Calories in the portions were then calculated. Only 34% of volume and 22% of calorie estimates were within 25% of their actual amounts. Nearly half the volume estimates were more than 25% greater than actual amounts. Approximately one third of the calorie estimates were underestimated by 26% or more.