Summary.Diet variability influences the accuracy of the assessment of the relationship between nutrient intake and disease. The present study investigates intra‐ and inter‐individual variability in an infant population at 12 months. The mothers of 79 infants completed a 7‐day weighted food record. No significant difference in nutrient intake was observed between males and females. For some nutrients an intra‐/inter‐individual variability ratio<1 was found. Adjustment for total calorie intake slightly altered the intra‐/inter‐individual variability ratio of many nutrients. An error margin of 10% or less for calories can be expected within an 18‐day study. Most nutrients however would need to be studied for over 30 days to give an error margin ≤10%. For dietary cholesterol, vitamins A, B6, C, and E, bracketing the error within the 10% margin would require an unrealistic time frame. Adjustments for calorie intake reduced the number of days in the dietary record for some nutrients. A lower intra/inter‐individual variability ratio was seen when data for adults and older in