Calculate how many calories you should eat per day to lose weight. The 51Health Calorie Deficit Calculator uses your body data, activity level, and weight loss goal to estimate a safe and sustainable daily calorie intake.
Most accurate for modern populations. Recommended by most nutritionists.
Men:
BMR = (10 × weight) + (6.25 × height) - (5 × age) + 5
Women:
BMR = (10 × weight) + (6.25 × height) - (5 × age) - 161
Classic formula revised in 1984. Still widely used and reliable.
Men:
BMR = 13.397W + 4.799H - 5.677A + 88.362
Women:
BMR = 9.247W + 3.098H - 4.330A + 447.593
Most accurate if you know your body fat percentage. Gender-neutral.
All:
BMR = 370 + (21.6 × LBM)
LBM = Lean Body Mass in kg
LBM = Weight × (1 - BF%/100)
A calorie deficit occurs when you consume fewer calories than your body burns in a day. This forces your body to use stored energy (primarily fat) to make up the difference, resulting in weight loss.
⚠️ Important: A calorie deficit should be sustainable and not too extreme. Eating too little can slow your metabolism, cause muscle loss, nutrient deficiencies, and make it harder to stick to your diet long-term.
Your daily calorie needs depend on several factors: your basal metabolic rate (BMR), activity level, age, gender, height, weight, and body composition. Here's a comprehensive breakdown:
Your BMR is the number of calories your body burns at complete rest just to maintain basic physiological functions like breathing, circulating blood, and cell production. This accounts for about 60-75% of your total daily energy expenditure.
Average BMR ranges:
Your TDEE is your BMR multiplied by an activity factor. This represents the total calories you burn in a day, including exercise, daily activities, and digestion (thermic effect of food).
TDEE = BMR × Activity Level
Average TDEE ranges:
TDEE - 10% to 25%
Create a sustainable deficit for fat loss
TDEE (exactly)
Maintain current weight
TDEE + 10% to 20%
Calorie surplus for building muscle
While creating a calorie deficit is necessary for weight loss, going too low can be counterproductive and dangerous. Here's what you need to know about safe deficit levels:
Best for: Preserving muscle, sustainable long-term
Weight loss: 0.25-0.5 kg/week
Best for: Steady progress, balanced approach
Weight loss: 0.5-0.75 kg/week
Best for: Faster results, short-term only
Weight loss: 0.75-1 kg/week
Risks: Muscle loss, metabolic slowdown, nutrient deficiencies
May not meet basic nutritional needs
Your body adapts to very low calories by slowing metabolism, making further weight loss harder.
Extreme deficits cause your body to break down muscle for energy, lowering your BMR.
Affects hunger hormones (leptin, ghrelin), thyroid function, and reproductive hormones.
Extreme hunger, low energy, and cravings make it nearly impossible to maintain long-term.
Calories burned per 30 minutes for a 70kg (154 lbs) person
Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182.
Katch FI, McArdle WD. Introduction to Nutrition, Exercise, and Health. 4th ed. Baltimore, MD: Lippincott Williams & Wilkins; 1993.
Hall KD, Heymsfield SB, Kemnitz JW, et al. Energy balance and its components: implications for body weight regulation. Am J Clin Nutr. 2012;95(4):989-994.
Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. Int J Obes (Lond). 2010;34 Suppl 1(Suppl 1):S47-S55.
U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2023.