Find your BMR and TDEE to calculate the exact calorie deficit for 1-2 lbs per week weight loss. Uses Mifflin-St Jeor equation | Calculator4U
Calculate your Basal Metabolic Rate and daily calorie needs for effective weight loss using Mifflin-St Jeor and Harris-Benedict formulas.
A BMR calculator for weight loss determines your Basal Metabolic Rate — the calories your body burns at complete rest — and uses it to calculate the exact daily calorie deficit needed to lose 1 to 2 pounds per week safely and sustainably. The Mifflin-St Jeor equation, recommended by the Academy of Nutrition and Dietetics, estimates BMR to within 10% accuracy of laboratory measurement for most adults. A moderately active 35-year-old woman at 5 foot 5 and 165 pounds has a BMR of approximately 1,484 calories and a TDEE of approximately 2,300 calories. Eating 1,800 calories per day creates a 500-calorie daily deficit for consistent 1 pound per week fat loss.
BMR accounts for 60 to 70% of everything you burn in a day — far more than exercise, which most people overestimate. Physical activity adds approximately 20% on top of BMR, and the thermic effect of digesting food adds another 10%. This means a person who does not exercise still burns the vast majority of their daily calories just keeping their body alive. Understanding your BMR tells you the minimum your body needs and sets the floor below which you should never reduce your intake — regardless of how much weight you want to lose.
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, and cell production. The Mifflin-St Jeor formula calculates BMR as: Men: BMR = 10×weight(kg) + 6.25×height(cm) - 5×age + 5. Women: BMR = 10×weight(kg) + 6.25×height(cm) - 5×age - 161. For weight loss, you need to eat below your TDEE (BMR × activity multiplier) to create a calorie deficit.
To lose weight safely, create a calorie deficit of 500-1000 calories per day below your TDEE. A 500-calorie daily deficit results in approximately 0.5 kg (1 lb) of weight loss per week, while a 1000-calorie deficit leads to about 1 kg (2 lbs) per week. Never eat below 1200 calories (women) or 1500 calories (men) without medical supervision, as this can slow metabolism and cause nutrient deficiencies.
BMR is calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) includes all daily activities. TDEE = BMR × Activity Multiplier. Multipliers are: Sedentary (1.2), Light exercise (1.375), Moderate exercise (1.55), Active (1.725), Very Active (1.9). For example, if your BMR is 1600 and you exercise moderately, your TDEE is 1600 × 1.55 = 2480 calories.
BMR is measured under strict lab conditions — completely still, fully rested, digestive system inactive. RMR is measured in a relaxed but not fully inactive state and runs 10 to 20% higher than true BMR. Most online calculators including this one calculate RMR using the Mifflin-St Jeor formula but refer to it as BMR because the terms are used interchangeably in everyday health practice. For weight loss planning, the distinction is minor — both give an accurate enough baseline.
Yes — severe calorie restriction can reduce BMR by up to 30% as your body adapts to conserve energy. This metabolic adaptation is why very low calorie diets often stop working after a few weeks. A moderate deficit of 500 to 750 calories per day causes significantly less metabolic slowdown than aggressive deficits above 1,000 calories. Maintaining high protein intake and resistance training during weight loss minimizes BMR reduction by preserving muscle mass.
NEAT or Non-Exercise Activity Thermogenesis is calories burned through all non-exercise movement — walking, fidgeting, standing, and daily tasks. It accounts for 15 to 30% of total daily energy expenditure and varies by up to 2,000 calories per day between individuals with the same BMR. Increasing daily steps to 8,000 to 10,000, using a standing desk, and taking walking breaks all boost NEAT significantly and support weight loss without additional formal exercise.
BMR declines approximately 1 to 2% per decade after age 20, primarily from muscle mass loss. A 60-year-old has roughly 8 to 15% lower BMR than a 20-year-old of identical height and weight — meaning they need fewer daily calories. This explains why the same diet that caused weight loss at age 30 may not work at 50. Resistance training to preserve and rebuild muscle is the most effective strategy for maintaining BMR with age, alongside recalculating your calorie targets every decade.