BMR / TDEE / Macro Calculator 2026

How this calculator works

BMR — Mifflin-St Jeor (2026 standard)

The Mifflin-St Jeor equation is the most-accurate predictor of BMR vs measured indirect calorimetry per multiple meta-analyses. Men: 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5. Women: 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161.

TDEE — Activity Multiplier

Sedentary 1.2 / Light 1.375 / Moderate 1.55 / Active 1.725 / Very Active 1.9. Most desk-job adults underestimate by selecting "moderate" — be honest. If you sit 8+ hrs/day with 3 gym sessions/week, you are LIGHT (1.375), not moderate.

Calorie deficit / surplus math

1 lb fat = ~3,500 kcal. Lose 1 lb/week = -500 kcal/day deficit. Lose 1.5 lb/week = -750 kcal/day. SUSTAINED deficit greater than 1,000 kcal/day risks muscle loss + metabolic adaptation.

Protein recommendations

ISSN 2024 position: 0.7-1.0 g/lb body weight for general health, 1.0-1.5 g/lb for muscle gain or aggressive cut + intense training. Older adults (50+) skew higher to fight sarcopenia.

Limitations

• Mifflin-St Jeor is a population estimate. Actual BMR can vary ±10% individual
• Body composition matters: 200 lb at 30% BF burns less than 200 lb at 15% BF (lean mass drives BMR)
• Metabolic adaptation: prolonged deficit reduces BMR 5-15% (adaptive thermogenesis)
• Activity multiplier varies hugely individual — best estimate by tracking + adjusting weekly
• Special populations (pregnancy, lactation, recovery from illness, growing teens) have different needs