Calorie Needs Calculator
BMR and TDEE by the Mifflin-St Jeor equation — the formula dietitians actually use — plus sensible targets for each goal.
Calculate your daily calories
BMR, TDEE, and the formula behind the numbers
Your BMR (basal metabolic rate) is what your body burns at complete rest — keeping you warm, breathing, thinking. Your TDEE (total daily energy expenditure) multiplies that by an activity factor to cover real life. This calculator uses the Mifflin-St Jeor equation, which research has found the most accurate of the common formulas:
A worked example
A 40-year-old man, 5'10", 180 lb, lightly active: BMR comes to about 1,755 calories, TDEE about 2,415. To lose roughly a pound per week he'd target ~1,915 (a 500-calorie deficit, since a pound of fat is ~3,500 calories); to gain lean mass slowly, ~2,665. These are starting points — the real test is what your scale does over 3–4 weeks, after which you adjust by 100–200 calories.
The mistakes that break calorie math
Three classics: overstating activity (a desk job plus three gym visits is "light," not "very active" — the gym hour doesn't cancel the other 23), under-tracking intake (oils, sauces, and bites add up to hundreds of invisible calories), and crash deficits — cutting far below BMR loses muscle, tanks energy, and rebounds. A moderate deficit you can sustain for months beats an aggressive one you abandon in two weeks, every single time.
Frequently asked questions
Why do different calculators give different numbers?
Different formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and rounding. They're all estimates within ~10%; your real-world weight trend over a few weeks is the ground truth that calibrates the number.
Should I eat below my BMR to lose faster?
Generally no. Aggressive deficits below BMR tend to cost muscle, energy, and adherence. A 500-calorie deficit from TDEE — roughly a pound a week — is the sustainable standard.
Do I need to eat back exercise calories?
If you chose an activity level that already includes your exercise, no — they're baked in. Counting them twice (in the multiplier AND eating them back) is one of the most common stalls.
How accurate are these numbers?
Within about 10% for most people; metabolism varies with genetics, muscle mass, and hormones. Use the result as a 3-week experiment: track honestly, weigh consistently, and adjust based on what actually happens. For medical conditions, work with a doctor or registered dietitian.
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The formula behind your calorie needs — TDEE explained
Your Total Daily Energy Expenditure (TDEE) is calculated in two steps. First, your Basal Metabolic Rate (BMR) — the calories burned at complete rest to maintain organ function, body temperature, and cellular repair. Second, an activity multiplier accounting for how much you move.
This calculator uses the Mifflin-St Jeor equation, the most accurate BMR formula for most adults per a 2005 systematic review in the Journal of the American Dietetic Association:
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Activity multipliers: Sedentary = BMR × 1.2. Lightly active (1–3 days/week) = BMR × 1.375. Moderately active (3–5 days/week) = BMR × 1.55. Very active (6–7 days) = BMR × 1.725. Extra active (physical job + training) = BMR × 1.9.
Worked examples with real numbers
Example 1 — 35-year-old woman, 5'6", 145 lb, moderately active: BMR = (10 × 65.8) + (6.25 × 167.6) − (5 × 35) − 161 = 658 + 1,047.5 − 175 − 161 = 1,369.5. TDEE = 1,369.5 × 1.55 = 2,123 calories/day. To lose 1 lb/week: eat about 1,623 cal/day.
Example 2 — 45-year-old man, 5'10", 195 lb, lightly active: BMR = (10 × 88.5) + (6.25 × 177.8) − (5 × 45) + 5 = 885 + 1,111.25 − 225 + 5 = 1,776. TDEE = 1,776 × 1.375 = 2,442 calories/day. At 500-calorie deficit: eat 1,942 cal/day to lose about 1 lb/week.
How to use calorie targets effectively
For weight loss
A 500-calorie daily deficit produces roughly 1 lb/week (3,500 calories ≈ 1 lb of fat). Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision — deficits that low trigger metabolic adaptation and muscle loss. Sustainable loss is typically 0.5–1% of body weight per week.
For muscle gain
Building muscle requires a calorie surplus — typically 250–500 calories above TDEE. Combined with adequate protein (0.7–1.0g per pound of body weight) and progressive resistance training, this supports muscle protein synthesis. A "lean bulk" targets the lower surplus to minimize fat gain.
For maintenance
Eating at TDEE stabilizes weight. Given that TDEE calculators have roughly ±10–15% individual variation, the most accurate approach is eating at your calculated TDEE for 2–3 weeks and adjusting based on actual weight trends.
Macronutrient distribution
Calories come from protein (4 cal/gram), carbohydrates (4 cal/gram), and fat (9 cal/gram). Common starting points:
- Protein: 25–35% of total calories, or 0.7–1.0g per pound of body weight. Most important macro for body composition regardless of goal.
- Fat: 20–35% of total calories. Supports hormone production, fat-soluble vitamin absorption, and satiety. Do not drop below 20% long-term.
- Carbohydrates: The remainder. Fuel high-intensity training and recovery.
Use the Macro Calculator to translate your calorie target into specific gram targets.
Las Vegas summer — the heat factor
Las Vegas summer heat (June–September, regularly 105–115°F) increases calorie expenditure through thermoregulation — your body burns additional calories keeping cool through sweating. The increase is modest (roughly 100–250 extra calories/day during intense heat exposure) but real. More significantly, heat suppresses appetite in many people, leading to unintentional undereating during summer months. Hydration also affects appetite regulation — dehydration mimics hunger. See the Water Intake Calculator for Las Vegas-appropriate hydration targets.
Frequently asked questions
Why does this calculator differ from other TDEE calculators?
Different calculators use different BMR formulas. The most common are Mifflin-St Jeor (used here — most accurate for most adults), Harris-Benedict (original 1919 formula, tends to overestimate), and Katch-McArdle (uses lean body mass — most accurate if you know your body fat percentage). Expect results within 100–200 calories of each other. All are estimates with ±10–15% individual variation.
How many calories should I eat to lose weight?
Start at your TDEE minus 500 calories for approximately 1 lb/week. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision. Larger deficits accelerate initial loss but increase muscle loss and metabolic adaptation. Sustainable loss is 0.5–1% of body weight per week.
Why am I not losing weight eating at a deficit?
Most common reasons: calorie tracking error (most people underestimate by 20–50%), water retention masking fat loss on the scale, or the deficit is smaller than calculated. Weigh food with a kitchen scale for 1–2 weeks to establish a true baseline. The scale reflects trends over weeks, not daily fluctuations.
Do I need to count calories to lose weight?
No — but it is the most reliable method because it creates awareness of intake. Alternatives that work: eliminating processed foods, portion control, or intuitive eating. Whatever creates a sustainable deficit produces results. Counting is a tool, not a requirement.
How does age affect calorie needs?
TDEE decreases 1–2% per decade after age 30, primarily due to declining muscle mass reducing BMR. The fix: resistance training to preserve muscle mass. A 55-year-old who strength trains 3x/week has meaningfully higher TDEE than a sedentary 55-year-old at the same body weight.
Are calories from different foods equal?
Calorically yes — a calorie is a unit of energy regardless of source. Metabolically and in terms of satiety and hunger hormones, different foods behave very differently. 400 calories of chicken and vegetables versus 400 calories of soda affect blood sugar, subsequent appetite, and satiety completely differently. Calories matter; food quality matters alongside them.
Disclaimer: This calculator provides general educational information only. Calorie needs vary significantly between individuals. Consult a registered dietitian or physician before making significant dietary changes, especially if you have a medical condition.