Free tools · Calorie & protein math
Calorie Deficit & Protein Calculator
Enter your sex, age, height, weight, activity level, and goal to estimate a daily calorie target for weight loss and a protein range that helps protect lean muscle while you're in a deficit. The math uses the validated Mifflin-St Jeor equation and is shown transparently so you can check every step. These are estimates, not a meal plan.
Read before you use this
This is an educational estimate, not medical or nutrition advice. The Mifflin-St Jeor equation predicts the energy needs of an average person; your real metabolism can run meaningfully higher or lower depending on body composition, genetics, medications, medical conditions, and how active you truly are. Use the number as a starting point and adjust based on how your weight actually changes over 2–4 weeks. Do not eat below the floored minimum the tool shows (about 1200 kcal for women, 1500 for men) without supervision — very-low-calorie diets can cost you muscle, bone, and nutrients. This tool is not appropriate for anyone who is pregnant or breastfeeding, under 18, has an eating disorder history, or has a chronic condition. Before making a large change to how you eat, talk to a licensed clinician or registered dietitian.
Daily calorie target
1651kcal / day
from a maintenance estimate of 2201 kcal minus a 550 kcal deficit (about 0.5 kg / week).
Daily protein target
120–165g / day
1.6–2.2 g per kg of body weight (75 kg). The higher end helps preserve lean muscle while you're in a calorie deficit — protein needs go up, not down, when you're losing weight.
- BMR
- 1420 kcal
- Resting energy (Mifflin-St Jeor)
- TDEE
- 2201 kcal
- BMR × 1.55 (activity)
- Daily deficit
- −550 kcal
- ≈ 0.5 kg/wk (7700 kcal/kg)
How it is calculated. Resting energy (BMR) uses the validated Mifflin-St Jeor equation: for men, 10×kg + 6.25×cm − 5×age + 5; for women, the same minus 161 (Mifflin MD et al., Am J Clin Nutr 1990). Total daily energy expenditure (TDEE) = BMR × an activity multiplier (1.2 sedentary to 1.9 extra active). A weekly loss of 0.25 / 0.5 / 0.75 kg needs roughly a 275 / 550 / 825 kcal daily deficit (≈7700 kcal per kg). The target is floored at 1200 kcal (women) / 1500 kcal (men). Protein is shown at 1.6–2.2 g/kg of body weight. Worked example: a 40-year-old woman, 165 cm, 75 kg, moderate activity, 0.5 kg/wk → BMR 1420, TDEE 2201, target 1651 kcal, protein 120–165 g.
Make the deficit easier to stick to
A calorie number is the easy part — appetite is the hard part. These honest, evidence-led reviews cover what actually helps with hunger and metabolic support, and where the science is weaker than the marketing:
Source. Resting energy expenditure is estimated with the Mifflin-St Jeor equation: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. “A new predictive equation for resting energy expenditure in healthy individuals.” American Journal of Clinical Nutrition, 1990;51(2):241–247 (PMID 2305711). Activity multipliers and the ≈7700 kcal-per-kg energy-deficit figure are standard nutrition-science conventions; protein at 1.6–2.2 g/kg reflects common recommendations for preserving lean mass during energy restriction. This calculator is informational and not medical advice — it does not account for your individual health, body composition, or clinical circumstances. Talk to a licensed clinician or registered dietitian before making large changes to how you eat.