Question 1

What is BMR and how is it calculated?

Accepted Answer

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell repair, body-temperature regulation. We use the Mifflin-St Jeor equation (1990), which the American Dietetic Association recommends as the most accurate option for non-obese adults: BMR = 10·weight(kg) + 6.25·height(cm) − 5·age(yr) + 5 (men) or − 161 (women). It is more accurate than the older Harris-Benedict equation for modern populations.

Question 2

What is the difference between BMR and TDEE?

Accepted Answer

BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for all daily movement: standing, walking, exercise, manual labour, even fidgeting. A sedentary office worker has TDEE ≈ BMR × 1.2; a marathon runner training daily has TDEE ≈ BMR × 1.9. Use TDEE — not BMR — as your daily calorie reference; eating only your BMR will create a large deficit and is generally not advisable.

Question 3

How accurate are calorie calculators?

Accepted Answer

BMR equations are population averages with about ±10% variance for any given individual. Genetics, body composition (more muscle = higher BMR), hormones, medications, sleep quality, and gut microbiome all influence actual metabolism. Treat the calculator output as a starting point: track your weight and intake for 2-4 weeks, then adjust calories up or down by 100-200 if your weight is not trending where you want.

Question 4

Is my personal data sent to any server?

Accepted Answer

No. Every calculation — BMR, TDEE, goal targets — runs in your browser via JavaScript. Weight, height, age, sex, activity level — none of it ever leaves your device. Health data is sensitive personal information; treat any online calculator that asks for an email or makes a network call as untrustworthy.

Question 5

Why does the calculator use a deficit of 500 calories for 1 lb/week loss?

Accepted Answer

The classic rule is "1 pound of body fat = ~3,500 calories", so a 500-calorie daily deficit over 7 days equals 3,500 calories = 1 pound. This is an approximation: actual weight loss includes water, glycogen, and lean tissue, not just fat — and metabolism adapts downward as you lose weight. In practice, deficits of 500 kcal/day yield 0.5–1 lb/week loss on average, slower over time. For most people, a 500-kcal deficit is sustainable; larger deficits (1000+) risk muscle loss, fatigue, and unsustainability.

Question 6

Should I use the Mifflin-St Jeor or Harris-Benedict equation?

Accepted Answer

Mifflin-St Jeor. The original Harris-Benedict equation dates to 1919 and was based on a population of 239 mostly-male, mostly-young, mostly-white adults — narrow by modern standards. The Mifflin-St Jeor equation (1990) used a larger, more diverse cohort and produces results 5–10% lower than Harris-Benedict for most adults, which research shows is more accurate against indirect-calorimetry measurements. Some calculators offer both; ours defaults to Mifflin-St Jeor because the evidence favours it.

Question 7

How do I calculate calories for muscle gain vs fat loss?

Accepted Answer

Fat loss: TDEE − 250 to 500 calories/day. The lower deficit preserves more muscle. Lean muscle gain: TDEE + 250 to 500 calories/day with adequate protein (1.6–2.2 g/kg body weight) and progressive resistance training. Bigger surpluses (1000+) cause excessive fat gain. The 0.5 lb/week and 1 lb/week goals in our calculator align with these recommendations. Combine the calorie target with a protein target separately; the calorie number alone does not guarantee muscle vs fat partitioning.

Question 8

Why isn't my calculator-recommended calorie intake working?

Accepted Answer

Four most-common reasons. (1) Tracking inaccuracy: most people under-count by 20-30%. Weigh-and-log everything for two weeks to find your real intake. (2) Activity level overstated: people pick "very active" when they really mean "moderate". Be honest. (3) Metabolic adaptation: extended deficits lower BMR by 5-10%; take periodic diet breaks. (4) Genetic variance: if no progress after 4 weeks of accurate tracking, drop calories by 100 or add a daily walk; don't make dramatic changes.

Question 9

Does this calculator account for body composition (lean mass)?

Accepted Answer

No — the Mifflin-St Jeor equation uses only weight, height, age, and sex. The Katch-McArdle equation incorporates lean body mass directly and is more accurate for very lean or very muscular individuals — but it requires a body-fat measurement (DEXA, skin-fold caliper, or bioimpedance scale) which most people don't have. For 95% of users, Mifflin-St Jeor is the right default. If you know your body-fat percentage to within ±2%, calculate lean mass and use Katch-McArdle (BMR = 370 + 21.6 · lean mass in kg) for a tighter estimate.

Level	Multiplier	Definition
Sedentary	×1.2	Desk job, no formal exercise; under 5,000 steps/day
Lightly active	×1.375	Light exercise 1–3 days/week; 5,000–7,500 steps/day
Moderately active	×1.55	Moderate exercise 3–5 days/week; 7,500–10,000 steps/day
Very active	×1.725	Hard exercise 6–7 days/week; 10,000–12,500 steps/day
Extra active	×1.9	Physical job + daily training; 12,500+ steps/day

Macro	kcal / gram	Note
Protein	4	Most filling per calorie
Carbohydrate	4	Includes sugars, starches, fibre
Fat	9	Most energy-dense; essential for hormones
Alcohol	7	Often forgotten in daily totals
Fibre (subset)	2	Partially digested; counted as ~2 kcal/g

Free Calorie Calculator: BMR, TDEE, and Daily Goal Targets

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