Estimates of energy content of dry feeds used by the National Research Council (NRC, 2001) are based on equations to estimate truly digestible non-fiber carbohydrate (NFC), CP, fatty acids and NDF from composition of feed. Total digestible nutrients, digestible and metabolizable energy (ME) are then calculated from these fractions with appropriate corrections and adjustments. Although this approach is efficient for adult animals, errors may occur when calculating ME in calf starters (CS). Digestion of nutrients, but particularly starch and NDF, is low in young calves consuming little CS and with negligible rumen development. Apparent total-tract digestion (TTD) of ADF and NDF in calves fed > 0.8 kg/d MR are < 50% of estimates in calves fed < 0.8 kg/d until 12–13 wk (6–7 wk post-weaning). Although CS intake increases rapidly post-weaning, inability to digest CS nutrients may partially explain post-weaning depressions in BW gain in the first few weeks post-weaning when calves are fed > 0.8 kg/d MR. Further, nutrient content of CS may influence TTD of nutrients. Calves fed a 41% starch, texturized CS had lower ADF and NDF digestion at 8 wk (1 wk post-weaning) compared with calves fed a 10% starch, pelleted CS, which may be due to low ruminal pH and depression of fiber digestion. We calculated ME in CS fed to Holstein bull calves from 0 to 16 wk using TTD data from 3 published studies. Calves were fed varying amounts of MR, and water and CS were available ad libitum. The TTD of NDF, NFC and total DM in CS increased with increasing NFC intake from CS in a logarithmic fashion. Calculated ME in CS in calves fed > 0.8 kg/d of MR (lower CS intake) were lower than calves fed less MR (greater CS intake) at similar ages. Natural logarithm of NFC intake from CS accounted for 70% of variation in calculated ME in CS. Calculated ME in CS was < 75% of NRC estimated ME when calves consumed 0.2 kg/d of NFC and 98% of NRC estimated ME when calves consumed 1 kg/d of NFC. Ability of the calf to extract energy from CS changes with age and rumen development and depends on intake of NFC from CS. Feeding management that delays NFC intake may reduce ME in CS. Equations using NFC intake may provide greater accuracy in estimating ME in CS.