Child Daily Nutrition Calculator
Calculates estimated daily calorie needs for children using a modified Harris-Benedict equation adjusted for weight, height, age, sex, and activity level. Useful for parents and dietitians planning balanced meals for growing kids.
About this calculator
This calculator adapts the Harris-Benedict equation, originally derived for adults, to estimate a child's Basal Metabolic Rate (BMR): BMR = 88.362 + (13.397 × weight_kg) + (4.799 × height_cm) − (5.677 × age_years). Weight in pounds is converted to kg (÷ 2.2046) and height in inches to cm (× 2.54) before use. The BMR is then multiplied by an activity factor — 1.2 for sedentary, 1.375 for light activity, 1.55 for moderate, and 1.725 for very active — to yield Total Daily Energy Expenditure (TDEE). A sex adjustment of ×0.9 is applied for girls, reflecting generally lower muscle mass relative to boys at the same age. The result is a personalized daily calorie target to support healthy growth without under- or over-fueling.
How to use
Example: a 10-year-old boy, 70 lbs, 52 inches tall, moderately active. Step 1 – Convert: 70 ÷ 2.2046 = 31.75 kg; 52 × 2.54 = 132.08 cm. Step 2 – BMR: 88.362 + (13.397 × 31.75) + (4.799 × 132.08) − (5.677 × 10) = 88.362 + 425.36 + 634.27 − 56.77 = 1,091.2. Step 3 – Activity (moderate): 1,091.2 × 1.55 = 1,691 kcal/day. Step 4 – Gender (male): ×1.0 → 1,691 kcal/day. This is the estimated daily calorie target for this child.
Frequently asked questions
How many calories does a child need per day by age and activity level?
Calorie needs vary widely depending on a child's age, size, sex, and how active they are. A sedentary 6-year-old girl might need around 1,200 kcal/day, while a very active 12-year-old boy could need over 2,400 kcal/day. The Harris-Benedict-based formula used here accounts for weight, height, age, and activity level simultaneously to give a personalized estimate. These figures are starting points; growth spurts, illness, and sports seasons all cause natural fluctuations in appetite and need.
What is the Harris-Benedict equation and why is it used for children?
The Harris-Benedict equation estimates Basal Metabolic Rate — the calories needed just to keep the body functioning at rest — based on weight, height, and age. Originally validated for adults, it is frequently adapted for older children and adolescents as a practical approximation when more pediatric-specific tools are unavailable. It should be used with caution for children under 3, for whom dedicated pediatric growth-based equations are more appropriate. A registered dietitian can help interpret the result in the context of a child's growth chart and individual health history.
Why do girls need fewer calories than boys of the same age and size?
On average, girls have a higher proportion of body fat and a lower proportion of lean muscle mass than boys of the same age and weight, and muscle tissue burns more calories at rest than fat tissue does. Hormonal differences also play a role, particularly as children approach puberty. This calculator applies a 10% reduction in estimated calories for girls to reflect that physiological difference in energy expenditure. Individual variation is substantial, however, and a child's actual needs are best assessed by tracking growth over time rather than relying on a single calculation.