Bulking Calculator

Bulking targets start with maintenance calories. Enter a maintenance intake you have observed at a stable bodyweight, or estimate it using Mifflin–St Jeor: resting energy = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for the male equation, or −161 for the female equation. Multiply resting energy by the selected activity factor to estimate maintenance.

Target calories = maintenance × (1 + surplus percentage ÷ 100). Protein = bodyweight in kg × the chosen g/kg target. Fat grams = target calories × fat percentage ÷ 100 ÷ 9. Carbohydrate grams = (target calories − 4 × protein grams − 9 × fat grams) ÷ 4. Calculations use full precision; displayed calories and grams are rounded independently.

Using your bulking targets

A modest surplus supports training and weight gain, but gained weight is not all muscle. Training history, program quality, sleep, and individual response affect the outcome. Track a consistent 7-day average of morning bodyweight and review it alongside average intake over 2–4 weeks. Adjust gradually rather than reacting to a single weigh-in.

Activity multipliers and calorie adjustments are planning assumptions, not measured energy expenditure. The calculator does not predict an exact weekly change or completion date. These adult estimates are not designed for pregnancy, breastfeeding, or individualized medical nutrition needs.

Sources

• Mifflin et al.: resting energy expenditure equation (1990)
• ISSN position stand: protein and exercise (2017)
• Iraki et al.: nutrition recommendations for off-season bodybuilding (2019)