Teenage Calorie Needs — Estimate by Age and Size

Teenagers eat a lot because they are large, active and still growing — three things at once. The calculator below runs an adult equation, which is a reasonable rough guide for older teens and tends to read low; the numbers further down come from the equations written specifically for ages 3 to 18. Enter metric values: 140 lb is 63.5 kg, 5 ft 9 in is 175 cm.

The equations built for this age group

The 2023 Dietary Reference Intakes give separate prediction equations for children and adolescents. Running two typical 16-year-olds through them, with height in cm and weight in kg:

Teenager	Inactive	Low active	Active	Very active
Boy, 16, 5 ft 9 in (175 cm), 140 lb (63.5 kg)	2,723	2,874	3,185	3,555
Girl, 16, 5 ft 4 in (163 cm), 125 lb (56.7 kg)	2,042	2,263	2,408	2,712

A 14-year-old boy of 5 ft 6 in and 120 lb lands near 2,505 kcal inactive and 2,903 active; a 14-year-old girl of 5 ft 3 in and 112 lb, near 1,960 and 2,309. On top of any of those, the DRI adds a small allowance for the energy actually deposited as new tissue — about 20 kcal a day at ages 14 to 18, and 25 to 30 at ages 9 to 13.

Note how modest that growth allowance is. Building a body costs surprisingly little on a daily basis. What makes a teenager’s requirement high is the combination of adult-sized body and a higher activity level, not the growth line item.

Why the adult formula reads low

Adult equations were derived from adults, and they contain no growth term at all. For a 17- or 18-year-old the miss is small; at 13 or 14 it is meaningful, because the reference data behind adult resting-rate formulas simply does not include bodies at that stage.

There is a second, subtler reason. Doubly labeled water measurements across the life course show that energy expenditure, once adjusted for fat-free mass, is elevated through childhood and declines gradually to adult levels at about age 20. A teenager’s tissue is metabolically more expensive per pound than an adult’s, and no adult formula knows that. Treat any adult-formula result for a teenager as a lower bound.

Restriction is a decision for a clinician

Adolescence is when growth, bone accrual and hormonal development are still in progress, and it is also the peak-risk window for eating disorders. A calorie number is a poor tool to hand a teenager unsupervised. If weight is a genuine concern, the useful path runs through a pediatrician or registered dietitian who can look at growth curves, eating patterns and habits together — not through a target on a screen.

Where a calorie figure is genuinely useful is in the opposite direction: making sure an athletic teenager is eating enough. Under-fueling during heavy training carries real consequences for bone and hormonal health, which the calorie needs for athletes page covers.

The rest of the lifespan

Requirements do not drift much again until much later. The calorie needs for older adults page picks up the story at the other end, and the TDEE calculator explains the adult arithmetic in full.

This content is informational and does not replace evaluation by a pediatrician or registered dietitian.