A 500 kcal/day deficit = ~1 lb/week weight loss. A 300 kcal/day surplus = ~0.6 lb/week muscle gain potential.
3,500 kcal deficit = approximately 1 lb of fat lost.
Never drop below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.
Use this calculator as a starting point for any health or fitness goal that requires a numeric benchmark. The result is an estimate, not a diagnosis — but it provides a concrete figure to track against over time.
Many users apply adult health classifications to children and teenagers, which is incorrect. Paediatric norms for height, weight, BMI, and body composition are age-and-sex-specific. Use age-appropriate reference tools for anyone under 18.
A nurse calculates a patient's health metric during a routine assessment, then uses the result alongside other clinical indicators to contextualise the finding — correctly treating the number as one data point among several rather than a standalone answer.
A 500 kcal/day deficit (3,500/week) results in approximately 1 lb of fat loss per week.
100–300 kcal/day surplus (lean bulk) minimises fat gain while supporting muscle growth.
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