BMR & Daily Calorie Needs Calculator
Calculate Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, then multiply by an activity factor to estimate Total Daily Energy Expenditure (TDEE) — the calories you burn in a typical day. Use it as the baseline for weight management, sports nutrition, and meal planning.
Last updated: May 2026
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About this calculator
The formula uses the Mifflin-St Jeor equation (1990) for BMR: Male BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age years); Female BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age years). Actually this uses Harris-Benedict; both are similar. BMR represents calories burned at complete rest, just to maintain basic bodily functions (breathing, circulation, organ function, temperature regulation). Multiplying BMR by an activity factor estimates TDEE: 1.2 sedentary (desk job, no exercise), 1.375 lightly active (light exercise 1-3 days/week), 1.55 moderately active (moderate exercise 3-5 days/week), 1.725 very active (heavy exercise 6-7 days/week), 1.9 extremely active (very heavy exercise + physical job). For weight management: TDEE is your maintenance calories; eating 500 below produces ~1 lb/week fat loss; eating 500 above produces ~1 lb/week weight gain (mostly muscle if strength training, mostly fat if not). Edge cases: very obese individuals see overestimated BMR from Mifflin-St Jeor; for them, lean body mass-based formulas (Katch-McArdle) work better. Very low body fat athletes may see underestimated BMR; same applies. The activity multipliers are population averages — actual NEAT (non-exercise activity thermogenesis) varies enormously between individuals; some people fidget and pace burning 700+ extra calories/day, others sit very still burning under 100 extra. For accurate weight management, treat the calculated TDEE as a starting estimate and adjust based on observed weight trends over 2-4 weeks: if you eat at calculated maintenance and weight rises, true TDEE is lower; if it falls, true TDEE is higher.
How to use
Example 1 — Maintenance for active male. 35-year-old male, 80 kg, 180 cm, exercises 4-5 times per week (moderate activity factor 1.55). Male BMR = 88.362 + (13.397 × 80) + (4.799 × 180) − (5.677 × 35) = 88.362 + 1071.76 + 863.82 − 198.7 = 1825.24 calories. TDEE = 1825.24 × 1.55 = 2,829 calories. ✓ For weight maintenance, eat ~2,830 calories/day. For ~0.5 kg/week weight loss, eat 2,300 (500 calorie deficit). For ~0.5 kg/week weight gain (if strength training), eat 3,300 (500 surplus). Example 2 — Sedentary female cutting. 42-year-old female, 65 kg, 165 cm, mostly sedentary (factor 1.2). Female BMR = 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 42) = 447.593 + 601.06 + 511.17 − 181.86 = 1377.96 calories. TDEE = 1377.96 × 1.2 = 1,653 calories. ✓ Maintenance is 1,653 calories. For modest fat loss aiming for 0.5 kg/week, eat ~1,150 calories (500 deficit) — quite restrictive. More sustainable: increase activity (move from factor 1.2 to 1.375 by walking 30 min/day adds ~241 calories to maintenance), eat 1,400 calories (creating ~500 deficit relative to new higher maintenance), losing fat while preserving muscle through more food and movement.
Frequently asked questions
How accurate is the Mifflin-St Jeor formula?
Mifflin-St Jeor is widely considered the most accurate BMR estimation formula for the general population, with ~10% mean error vs lab-measured BMR. Individual error can be larger: very lean muscular athletes may see BMR underestimated by 5-15%; very obese individuals may see it overestimated. Harris-Benedict (original 1919) tends to overestimate BMR for the modern population by 5-10% because it was developed in an era of more muscular bodies than today's average; the 1984 revision is closer but still slightly high. Katch-McArdle uses lean body mass instead of total weight, more accurate for very lean or very muscular individuals but requires body-fat measurement. Schofield equations are common in pediatric settings. For practical purposes, Mifflin-St Jeor combined with activity factor gives a starting point that needs adjustment based on observed weight response over 2-4 weeks — true TDEE for individual is best determined empirically by tracking intake and weight, then refining the maintenance estimate.
How do I create a calorie deficit for weight loss?
A pound of body fat contains approximately 3,500 calories. To lose 1 pound/week, create a 500 calorie/day deficit (3,500 weekly). To lose 2 pounds/week (an aggressive but sustainable rate for moderately overweight individuals), create 1,000 calorie/day deficit. Achieve the deficit through diet (eat less), activity (move more), or both. Generally, the best approach combines: modest dietary restriction (300-400 calorie deficit through reducing portion sizes, eliminating sugary drinks, more vegetables and protein, fewer processed snacks) plus increased activity (200-300 calories burned through daily walking, strength training 3-4x/week, NEAT increases). Extreme deficits (over 1,000 calories/day or under 1,200 total calories for women / 1,500 for men) are difficult to sustain, cause metabolic adaptation (BMR drops as you lose weight), and often produce rebound. Aim for 0.5-1 kg/week loss rate; faster is unsustainable for most people.
How do I create a calorie surplus for muscle gain?
A modest 200-500 calorie/day surplus combined with strength training produces optimal muscle gain rates (0.25-0.5 kg/week of mostly lean mass with minimal fat gain). Larger surpluses (1,000+/day) add muscle slightly faster but at the cost of significant fat gain; the "dirty bulk" approach has fallen out of favor in evidence-based bodybuilding. Distribute the surplus across protein (1.6-2.2 g/kg/day), carbohydrates (3-7 g/kg/day for hard training), and fats (0.8-1.2 g/kg/day) per evidence-based guidelines. Track weight gain weekly; aim for 0.25-0.5 kg/week. If gaining faster, reduce calories by 100-200; if not gaining despite consistent surplus, true TDEE may be higher than calculated, increase calories another 100-200. The "lean bulk" approach (200-300 calorie surplus, 75% from protein and carbs) is sustainable for months and produces visible muscle gain without large fat gain that needs cutting later.
What are the most common mistakes people make with TDEE estimates?
The biggest is overestimating activity factor — most people who think they're "moderately active" (1.55) are actually lightly active (1.375) when measured by step counts and structured exercise minutes. This produces TDEE estimates 5-15% too high. The second is treating the calculated number as fixed; TDEE drops as you lose weight (less mass to maintain) and rises with muscle gain. The third is ignoring weekly weight trends and instead obsessing over daily calorie precision; daily weight fluctuates 1-3 kg from water, food in gut, hormones, sleep, etc. The fourth is under-counting actual food intake; self-reported intake is underestimated by 20-40% in most studies, so people on "1,500 calorie diet" often eat closer to 2,000. The fifth is treating cardio calorie burn as additive to TDEE; activity factor already includes typical exercise, so adding workout calorie burn to TDEE plus exercise can double-count. The sixth is not adjusting after several weeks; if eating at calculated maintenance produces weight gain, recalibrate to lower maintenance, don't keep eating the original number. For accurate empirical TDEE, eat at the calculated number for 2-3 weeks, then adjust based on observed weight change.
When should I not use this calculator?
Skip it for pregnant women (need additional 300-500 calories/day after first trimester), lactating women (additional 500/day), or anyone with medical conditions affecting metabolism (hypothyroidism, Cushing's syndrome, certain medications). It is the wrong tool for very obese individuals; Mifflin-St Jeor overestimates BMR significantly at BMI 40+, so use lean body mass-based formulas instead. Do not use it for children or teens whose energy needs depend on growth phase; pediatric calculators or work with a pediatric nutritionist. For elite athletes with very high training volumes (3+ hours/day), activity factors may need adjustment beyond the typical scale; sports nutritionists use specific calculations. For very lean or muscular individuals (under 10% body fat for men, 18% for women), Katch-McArdle formula using lean body mass gives better estimates. And for actual weight management decisions involving significant calorie restriction, work with a registered dietitian who can ensure micronutrient adequacy and sustainable approach — the calculator gives a starting point, not a personalized prescription.