Calorie Calculator
Calculate daily calorie needs based on age, weight, height, gender, and activity level. Includes weight loss and gain targets.
Reviewed by the Calcura editorial team · Last reviewed
- Question
- How many calories do I need per day?
- Answer
- Calculate BMR with the Mifflin-St Jeor equation (10 × weight_kg + 6.25 × height_cm − 5 × age + s, where s = +5 for male, −161 for female), then multiply by an activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 active, 1.9 very active. A 35-year-old woman, 70 kg, 168 cm, moderately active, has BMR ≈ 1,418 and TDEE ≈ 2,198 kcal. For weight loss, subtract ~500/day for ~1 lb/week.
▸Show formula & caveatsHide formula & caveats
- Formula
TDEE = (10w + 6.25h − 5a + s) × activity_factor- Caveats
- Equation estimates can be off by ±200–400 kcal; adjust based on 2–4 weeks of real weight data.
- NEAT (non-exercise activity) varies widely — fidgeters can burn 500+ extra kcal/day.
- Underestimating portions and overestimating activity is the #1 cause of stalled weight loss; weigh food.
What This Calculator Does
This calculator estimates your daily calorie needs using the Mifflin-St Jeor equation for basal metabolic rate (BMR), then multiplies by a standard activity factor to produce total daily energy expenditure (TDEE). It then shows maintenance calories, a 500-calorie deficit target for ~1 lb/week weight loss, and a 500-calorie surplus for ~1 lb/week gain. Treat the numbers as a starting point, not a prescription — individual metabolism can vary ±200–400 calories from the equation estimate due to lean mass, non-exercise activity (NEAT), and hormonal differences. Adjust based on two to four weeks of actual weight and measurement data.
When To Use This Calculator
Starting a weight-loss plan with a measured deficit
A 35-year-old woman, 165 lb, 5'5", moderately active gets a TDEE around 2,075 calories. A 500-calorie deficit puts her target at ~1,575 calories/day, a common starting point for ~1 lb/week loss that still allows meaningful nutrient intake.
Calibrating a bulk for muscle gain
A 22-year-old man, 160 lb, 5'10", training 4–5 days/week has a TDEE near 2,750. A 300–500 calorie surplus (3,050–3,250) supports lean mass gain without excessive fat accumulation, assuming adequate protein and progressive training.
Returning to tracking after a weight plateau
After losing 15 lb and stalling, your new TDEE at the lower weight is lower too. Re-running the calculator with current weight often shows the 'old' deficit is now closer to maintenance, explaining the plateau.
Deciding whether a calorie goal from a fitness app is reasonable
If an app says 1,100 calories/day for a 180 lb adult, cross-check here. TDEE around 2,400–2,600 means 1,100 is an aggressive 50%+ deficit — likely to drive muscle loss and metabolic slowdown versus a more sustainable 500-calorie cut.
How It Works
BMR is calculated via the Mifflin-St Jeor equation, which research has found to be the most accurate of the common BMR formulas for non-obese adults. Weight and height are normalized to metric, and the sex offset is +5 for men and −161 for women. TDEE multiplies BMR by an activity factor: 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active), 1.9 (very active). The ±500 calorie weight loss/gain targets assume that 3,500 calories ≈ 1 lb of body fat — a rough rule of thumb that holds on average but varies in practice due to water, glycogen, and muscle changes.
Formula
BMR (men) = 10×kg + 6.25×cm − 5×age + 5
BMR (women) = 10×kg + 6.25×cm − 5×age − 161
TDEE = BMR × activity factorReal-World Example
Scenario
Maya is 32, 5'4" (163 cm), 155 lb (70.3 kg), works a desk job but lifts weights 3 days/week. She wants to lose ~1 lb/week without crashing her training.
Calculation
BMR: 10 × 70.3 + 6.25 × 163 − 5 × 32 − 161 = 703 + 1018.75 − 160 − 161 ≈ 1,401 cal Activity factor (light, 1.375): 1,401 × 1.375 ≈ 1,926 cal TDEE Weight-loss target: 1,926 − 500 ≈ 1,426 cal/day
Result
Maya's maintenance is about 1,930 calories; her weight-loss target is ~1,425 calories. At that intake with ~120 g protein/day, she should lose close to 1 lb/week over the first 4–6 weeks. If the scale moves faster (water loss) or slower, she adjusts by ±100–150 calories rather than slashing further.
Common Mistakes to Avoid
Mistake: Trusting the activity multiplier blindly
Solution: Most people overestimate their activity level. If you sit at a desk 8 hours and do 3 gym sessions per week, 'light' (1.375) or even 'sedentary' (1.2) is often more accurate than 'moderate' (1.55). The difference can be 300+ calories/day.
Mistake: Eating back exercise calories from a tracker
Solution: Apple Watch, Fitbit, and MyFitnessPal consistently overestimate exercise calorie burn — sometimes by 30–50%. If you're using TDEE (which already includes activity), don't add exercise calories on top. Use TDEE as the full daily target and let the activity multiplier do the work.
Mistake: Going below the 1,200/1,500 floor for quick loss
Solution: Very-low-calorie diets drive muscle loss, fatigue, hormonal disruption, and rebound weight gain. Published guidance (Academy of Nutrition and Dietetics) recommends staying above ~1,200 cal/day for women and ~1,500 for men unless under medical supervision.
Mistake: Not recalibrating after 10–15 lb of loss or gain
Solution: TDEE drops ~30–50 calories per 10 lb of weight loss, and adaptive thermogenesis can shave another 50–150 calories off. Re-run the calculator every 4–6 weeks or after notable weight changes to keep your deficit/surplus honest.
Calorie Calculator vs. Related Fitness Calculators
TDEE Calculator
The same Mifflin-St Jeor engine, but focused purely on maintenance calories without deficit/surplus framing. Useful when you just want to know your baseline burn.
Macro Calculator
Takes calorie targets and splits them into protein, carbs, and fat grams. Pair with this calculator once you know your daily calorie goal.
BMI Calculator
A crude screening tool for weight status relative to height. Useful for population-level framing but not a substitute for calorie planning.
When This Isn't the Right Tool
Medical conditions that alter metabolism
Use instead: Hypothyroidism, Cushing's, PCOS, and certain medications can shift actual TDEE by 10–20% from the equation estimate. Work with a registered dietitian or physician; indirect calorimetry is the gold standard for measurement.
Highly muscular or very lean bodies
Use instead: Mifflin-St Jeor doesn't use body composition. For bodybuilders, elite endurance athletes, or people with >30% body fat, the Katch-McArdle equation (which uses lean body mass) is typically more accurate.
Pregnancy, lactation, or growth
Use instead: Energy needs in pregnancy (+300 cal/day in 2nd/3rd trimester) and lactation (+450–500 cal/day) aren't captured here. For children and teens, the Dietary Reference Intakes use different equations that account for growth.
Severe obesity or post-bariatric surgery
Use instead: Equations validated on non-obese adults systematically overestimate BMR at very high BMIs. The Mifflin-St Jeor estimate can be 200–500 cal too high for BMI >40. Clinical guidance and measured resting metabolic rate testing are more appropriate.
How to Verify This Calculation
Cross-check against a second equation (Harris-Benedict, Katch-McArdle if you know body fat %). Estimates within ~5–10% of each other is expected. For real-world calibration: track intake for 2 weeks at estimated maintenance and weigh daily — if weight is stable within ±1 lb, the estimate is close enough.
Sources
- Mifflin-St Jeor Equation — original study — Mifflin et al. 1990 in the American Journal of Clinical Nutrition — the source equation for BMR used by this calculator.
- Academy of Nutrition and Dietetics — Energy Expenditure — AND's evidence-based nutrition guidance, including calorie recommendations and minimum intake thresholds.
- USDA Dietary Guidelines for Americans — Federal nutrition guidelines including estimated calorie needs by age, sex, and activity level.
Reviewed by the Calcura editorial team · Last reviewed