Last updated: May 2026
Find your daily calorie needs using the Mifflin-St Jeor equation, then log your meals below.
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Nutritional data from USDA FoodData Central. For informational purposes only.
This calculator uses the Mifflin-St Jeor equation - the most accurate BMR formula for most adults, validated by a 2005 meta-analysis in the Journal of the American Dietetic Association as more accurate than the older Harris-Benedict equation.
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. Your TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor: Sedentary (x1.2), Light activity (x1.375), Moderate (x1.55), Very active (x1.725), Extra active (x1.9).
Worked example: A 35-year-old woman, 5 feet 5 inches (165 cm), 145 lbs (66 kg), moderately active:
BMR = (10 x 66) + (6.25 x 165) - (5 x 35) - 161 = 660 + 1,031 - 175 - 161 = 1,355 calories/day
TDEE = 1,355 x 1.55 = 2,100 calories/day to maintain current weight.
A 500 calorie/day deficit yields approximately 1 lb/week of fat loss. A 1,000 calorie/day deficit yields roughly 2 lbs/week, which is generally the recommended maximum for sustainable weight loss.
A 2005 meta-analysis in the Journal of the American Dietetic Association found the Mifflin-St Jeor equation predicted BMR within 10% for 82% of people tested - more accurate than the older Harris-Benedict equation. However, no formula accounts for individual metabolic variation, muscle mass differences, or hormonal factors. Use your calculated TDEE as a starting point, then adjust by 100-200 calories based on real-world results tracked over 2-4 weeks.
BMR (Basal Metabolic Rate) is the energy your body burns doing absolutely nothing - maintaining heartbeat, breathing, body temperature, and cell function. TDEE (Total Daily Energy Expenditure) multiplies BMR by your activity level and is the number that actually matters for nutrition planning. Eating at your TDEE maintains weight; eating below it creates a calorie deficit for fat loss.
A deficit of 500 calories per day yields roughly 1 lb per week of fat loss; 1,000 calories per day deficit yields roughly 2 lbs per week. Most nutrition guidelines recommend no more than 1-2 lbs per week to preserve muscle mass and ensure adequate nutrition. Diets below 1,200 calories for women or 1,500 for men are not recommended without medical supervision due to risks of muscle loss and nutrient deficiency.
Not necessarily. Research shows calorie awareness correlates with better weight management even without strict tracking. However, studies consistently show people underestimate their calorie intake by 20-50%. Tracking calories for even 2-4 weeks builds accurate portion intuition that can guide food choices long-term without continued tracking. Apps like MyFitnessPal or Cronometer can make tracking straightforward if you choose that approach.
Your Total Daily Energy Expenditure (TDEE) is the number of calories your body needs each day to maintain its current weight, accounting for everything from keeping your heart beating to running a 5K. It is calculated by first estimating your Basal Metabolic Rate (BMR)—the calories burned at complete rest—then multiplying by an activity factor that reflects how much you move throughout the day. The Mifflin-St Jeor equation, validated in a landmark 2005 meta-analysis, predicts BMR within 10% for roughly 82% of people and is considered more accurate than the older Harris-Benedict formula.
The activity multiplier is often the most miscalibrated part of the calculation. Most office workers overestimate their activity level, and studies consistently find that people underreport food intake by 20–50%. If your weight is not changing in the direction you expect after two to four weeks of eating at your calculated TDEE, adjust by 100–200 calories and reassess rather than making large dramatic cuts that increase the risk of muscle loss and nutrient deficiency.
| Activity Level | Multiplier | Description | Example |
|---|---|---|---|
| Sedentary | ×1.2 | Little or no exercise | Desk job with no deliberate exercise |
| Lightly Active | ×1.375 | Light exercise 1–3 days/week | Daily walks plus occasional gym session |
| Moderately Active | ×1.55 | Moderate exercise 3–5 days/week | Gym 4× per week, active job |
| Very Active | ×1.725 | Hard exercise 6–7 days/week | Daily training, competitive sport |
| Extra Active | ×1.9 | Very hard exercise plus physical job | Athletes, construction workers, military |
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body needs to sustain basic life functions at complete rest—heartbeat, breathing, temperature regulation, and cell repair. TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor to account for movement throughout the day. TDEE is the number that actually governs weight change: eat below it to lose, above it to gain, and at it to maintain.
Which calorie formula is most accurate—Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle?
Mifflin-St Jeor is generally the most accurate for the general population, predicting BMR within 10% for about 82% of people. Harris-Benedict (revised 1984) is slightly less accurate. Katch-McArdle uses lean body mass instead of total weight and can be more accurate for lean, muscular individuals who know their body fat percentage. No equation replaces real-world tracking over several weeks.
How many calories do I need to cut to lose 1 pound per week?
One pound of fat contains approximately 3,500 calories, so a daily deficit of 500 calories produces roughly 1 lb of weight loss per week. In practice, the body adapts over time by reducing TDEE, so actual results may be slightly slower. Most guidelines recommend keeping deficits between 500–1,000 calories per day (1–2 lbs/week) to preserve muscle mass and avoid nutrient deficiencies.
Do calories from different foods matter equally for weight management?
For total weight change, a calorie is a calorie—energy balance is the primary driver. However, food quality significantly affects satiety, muscle retention, and metabolic health. Protein has the highest thermic effect (20–30% of calories are burned during digestion) and is most protective of lean mass during a deficit. Ultra-processed foods tend to be easier to overconsume and less satiating per calorie than whole foods.
Why does my calorie need change as I lose weight?
As body weight decreases, BMR falls because there is less tissue to maintain. Losing 20–30 lbs can reduce TDEE by 100–200 calories per day. This is why weight loss often plateaus: the deficit that worked initially shrinks as you get lighter. Recalculating your TDEE every 10–15 lbs lost and adjusting intake accordingly—or adding activity—keeps progress moving.