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Calorie Calculator

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How It Works

The Calorie Calculator estimates your daily maintenance calories (Total Daily Energy Expenditure, or TDEE) in two steps. First, it computes your Basal Metabolic Rate (BMR) — the energy your body burns at complete rest — using the Mifflin-St Jeor equation (1990), which is generally considered the most accurate prediction equation for healthy adults. Male BMR = 10·w + 6.25·h − 5·a + 5; Female BMR = 10·w + 6.25·h − 5·a − 161, where w is weight in kg, h is height in cm, and a is age in years. Second, it multiplies BMR by an activity factor (1.2 sedentary → 1.9 extra active) to estimate TDEE. The results table shows your daily target across five goals: moderate cut (TDEE − 500 ≈ 1 lb/week loss), mild cut (TDEE − 250), maintain (TDEE), mild bulk (TDEE + 250), and moderate bulk (TDEE + 500). The hero value is the maintenance number.

Example Problem

A 30-year-old man is 175 cm tall and weighs 70 kg. He works a desk job and trains moderately 4 days a week. How many calories should he eat to maintain his weight, and what target would produce roughly 1 lb/week of fat loss?

  1. Compute BMR with the male Mifflin-St Jeor equation: BMR = 10·w + 6.25·h − 5·a + 5.
  2. Substitute: BMR = 10 × 70 + 6.25 × 175 − 5 × 30 + 5.
  3. Simplify each term: 700 + 1093.75 − 150 + 5.
  4. Sum: 700 + 1093.75 = 1793.75; 1793.75 − 150 = 1643.75; 1643.75 + 5 = 1648.75 kcal/day.
  5. Apply the moderately active factor (1.55) to get TDEE: 1648.75 × 1.55 ≈ 2556 kcal/day — the daily intake to maintain weight.
  6. For ~1 lb/week loss, subtract 500 kcal/day: 2556 − 500 = 2056 kcal/day target. For a mild cut subtract 250 instead: 2306 kcal/day.

Key Concepts

BMR is your resting energy floor — the calories your body would burn if you stayed in bed all day. TDEE adds the cost of habitual movement on top: light fidgeting, walking around the house, deliberate exercise, and the thermic effect of food (the ~10% of calories spent digesting meals). The activity multipliers are population averages, not exact measurements: sedentary 1.2 (desk job, no exercise), light 1.375 (light exercise 1–3 days/week), moderate 1.55 (3–5 days/week), active 1.725 (hard exercise 6–7 days/week), and very active 1.9 (twice-daily training or a physically demanding job). The 3,500-kcal-per-pound rule of thumb says a 500 kcal/day deficit drives roughly 1 lb/week of fat loss — in practice, metabolic adaptation slows that rate after a few weeks, so re-measure every 2–4 weeks and adjust. Mifflin-St Jeor was derived on healthy adults aged 19–78; it's not recommended for children, pregnant or lactating women, or critically ill patients, where measured indirect calorimetry is preferred.

Applications

  • Setting a daily calorie target for weight loss, maintenance, or gain.
  • Macro planning — once you know your kcal target, allocate to protein/carbs/fat by goal (cutting: protein 1.6–2.2 g/kg, deficit from carbs and fat).
  • Sports nutrition for athletes adjusting intake across training cycles.
  • Bariatric and clinical weight-management programs that need a fast estimate before a measured RMR test.
  • Educational tool for understanding why two people with the same weight can have very different calorie needs (height, age, and sex all matter).

Common Mistakes

  • Overestimating activity level. Most people think they're 'moderately active' when they're actually closer to sedentary — choose the next factor down if you mostly sit during work hours, even if you exercise 3 times a week.
  • Trying to lose weight too fast. Cuts beyond 500–750 kcal/day below TDEE often backfire: muscle loss, fatigue, poor adherence, and rebound weight gain. A 0.5–1% body-weight loss per week is sustainable.
  • Treating the calorie number as exact. Prediction equations carry ±10% error vs. measured RMR. Use the number as a starting point, log intake for 2 weeks, and adjust based on real-world weight change.
  • Forgetting that exercise calories are already partially in your activity multiplier. Eating back every calorie a fitness tracker reports on top of TDEE typically erases the deficit.
  • Eating below ~1,200 kcal/day (women) or ~1,500 kcal/day (men) without medical supervision. Very-low-calorie diets risk nutrient deficiencies and gallstones; clinicians monitor electrolytes and bone health.
  • Using Mifflin-St Jeor for children, pregnant women, or critically ill patients. Different equations apply to those populations.

Frequently Asked Questions

How do you calculate daily calories?

Compute BMR with Mifflin-St Jeor: Male BMR = 10·w + 6.25·h − 5·a + 5; Female BMR = 10·w + 6.25·h − 5·a − 161 (w in kg, h in cm, a in years). Multiply BMR by an activity factor (1.2 sedentary → 1.9 very active) to get TDEE, your daily maintenance calories. For weight loss, subtract 250–500 kcal/day from TDEE; for gain, add 250–500.

What is TDEE?

TDEE (Total Daily Energy Expenditure) is the total kilocalories your body burns in 24 hours, including resting metabolism, the thermic effect of food, and all movement. TDEE = BMR × activity factor. Eating at your TDEE keeps weight stable; eating below it produces fat loss, and eating above it produces weight gain.

How many calories should I eat per day?

It depends on your BMR, activity level, and goal. For weight maintenance, eat at your TDEE (typically 2,000–2,500 kcal/day for adult men and 1,600–2,000 kcal/day for adult women). For roughly 1 lb/week of fat loss, eat 500 kcal/day below TDEE. For lean muscle gain, eat 200–500 kcal/day above TDEE while resistance training.

How accurate is the Mifflin-St Jeor equation?

Mifflin-St Jeor (1990) is considered the most accurate of the common prediction equations for healthy adults — it predicts measured RMR within ±10% for about 80% of people. It's modestly more accurate than the older Harris-Benedict equation, especially for overweight and obese adults. For exact numbers, indirect calorimetry under clinical conditions is the gold standard.

Why does my activity factor matter so much?

Because BMR is only about 60–75% of TDEE for most adults — activity makes up the rest. The difference between sedentary (1.2) and very active (1.9) is roughly 1,200 kcal/day for a person with a 1,700-kcal BMR. Picking the wrong activity level is one of the largest sources of error in calorie targeting, so be honest: most desk-bound people who exercise 3 times a week land between 'lightly active' and 'moderate', not 'very active'.

What's a safe calorie deficit for weight loss?

A daily deficit of 250–500 kcal below TDEE produces 0.5–1 lb/week of fat loss for most adults — sustainable, preserves muscle if paired with strength training and adequate protein, and rarely triggers severe metabolic adaptation. Larger deficits (750–1,000 kcal/day) work short-term but increase muscle loss, fatigue, and the odds of regain. As a floor, women generally shouldn't go below ~1,200 kcal/day and men below ~1,500 kcal/day without medical supervision.

Should I eat back exercise calories?

Usually no — at least not all of them. Your chosen activity multiplier already accounts for habitual exercise (the difference between sedentary 1.2 and active 1.725 is the calories burned in regular workouts). Fitness-tracker estimates of single-session burn are often inflated by 20–30%, so eating back every reported calorie typically erases the deficit. If you do a workout well outside your usual routine (a long hike, a marathon), adding partial fuel back (about half the estimated burn) is reasonable.

What's the difference between BMR, RMR, and TDEE?

BMR (Basal Metabolic Rate) is measured under strict conditions: 12-hour fast, fully rested, thermoneutral environment. RMR (Resting Metabolic Rate) is measured under less strict conditions and runs about 10% higher than BMR — most prediction equations and consumer calculators actually estimate RMR even when labeled 'BMR'. TDEE is BMR (or RMR) multiplied by an activity factor that captures all non-resting energy expenditure.

Worked Examples

Fat Loss — Moderate Cut

How many calories should a 35-year-old woman eat to lose about 1 lb/week?

A 35-year-old woman is 165 cm tall and weighs 75 kg. She walks daily and lifts weights 3 times a week (lightly active). What is her TDEE, and what daily target produces roughly 1 lb of fat loss per week?

  • Knowns: sex = female, weight w = 75 kg, height h = 165 cm, age a = 35 years, activity factor = 1.375.
  • Apply the female Mifflin-St Jeor equation: BMR = 10w + 6.25h − 5a − 161.
  • Substitute: BMR = 10 × 75 + 6.25 × 165 − 5 × 35 − 161 = 750 + 1031.25 − 175 − 161 = 1,445.25 kcal/day.
  • Multiply by the lightly active factor: TDEE = 1,445.25 × 1.375 ≈ 1,987 kcal/day.
  • For ~1 lb/week loss subtract 500 kcal/day: 1,987 − 500 ≈ 1,487 kcal/day target.

TDEE ≈ 1,987 kcal/day · 1 lb/week loss target ≈ 1,487 kcal/day

1,487 kcal/day is close to the 1,200-kcal floor many clinicians recommend for women — staying within 200 kcal of the floor is acceptable short-term but monitor energy, sleep, and menstrual function. A mild cut (TDEE − 250 ≈ 1,737 kcal/day) is gentler and easier to sustain long-term.

Lean Bulk — Strength Training

What's the bulking calorie target for a 25-year-old man lifting 4 days a week?

A 25-year-old man is 180 cm tall and weighs 80 kg. He lifts heavy 4 days a week and walks on rest days (moderately active). What is his maintenance TDEE, and what should he eat to gain about 0.5 lb/week of mostly lean mass?

  • Knowns: sex = male, weight w = 80 kg, height h = 180 cm, age a = 25 years, activity factor = 1.55.
  • Apply the male Mifflin-St Jeor equation: BMR = 10w + 6.25h − 5a + 5.
  • Substitute: BMR = 10 × 80 + 6.25 × 180 − 5 × 25 + 5 = 800 + 1125 − 125 + 5 = 1,805 kcal/day.
  • Multiply by the moderately active factor: TDEE = 1,805 × 1.55 ≈ 2,798 kcal/day.
  • Add a mild surplus for lean gain: 2,798 + 250 ≈ 3,048 kcal/day target.

TDEE ≈ 2,798 kcal/day · mild-bulk target ≈ 3,048 kcal/day

A 250 kcal/day surplus with structured resistance training and 1.6–2.2 g/kg protein favors lean mass gain over fat. Larger surpluses (500+ kcal) work but add more fat per pound. Track weight weekly — if you're gaining more than ~0.75 lb/week, trim 100–200 kcal.

Sedentary Maintenance

What is the daily calorie need for a 55-year-old sedentary woman?

A 55-year-old woman is 160 cm tall and weighs 68 kg. She works a desk job, drives to work, and does not exercise. What is her maintenance calorie target?

  • Knowns: sex = female, weight w = 68 kg, height h = 160 cm, age a = 55 years, activity factor = 1.2 (sedentary).
  • Apply the female Mifflin-St Jeor equation: BMR = 10w + 6.25h − 5a − 161.
  • Substitute: BMR = 10 × 68 + 6.25 × 160 − 5 × 55 − 161 = 680 + 1000 − 275 − 161 = 1,244 kcal/day.
  • Multiply by the sedentary factor: TDEE = 1,244 × 1.2 ≈ 1,493 kcal/day.
  • Eating at ≈1,493 kcal/day maintains current weight; subtract 250 for a slow, sustainable loss (≈1,243 kcal/day).

TDEE ≈ 1,493 kcal/day · mild-cut target ≈ 1,243 kcal/day

Adding even modest daily walking (30 minutes) typically nudges the activity factor up to 1.375 — that alone adds about 220 kcal/day to maintenance, which can erase a small deficit. Activity factor is the single largest lever on TDEE.

Calorie Formulas (Mifflin-St Jeor + Activity Factor)

Daily maintenance calories — also called Total Daily Energy Expenditure (TDEE) — is the number of kilocalories your body burns in 24 hours, including resting metabolism, movement, exercise, and digestion. This calculator estimates TDEE in two steps:

BMR = 10·w + 6.25·h − 5·a + 5Men (Mifflin-St Jeor, 1990)
BMR = 10·w + 6.25·h − 5·a − 161Women (Mifflin-St Jeor, 1990)
TDEE = BMR × activity factor

Where:

  • BMR — basal metabolic rate in kilocalories per day (kcal/day)
  • w — body weight in kilograms (kg)
  • h — standing height in centimeters (cm)
  • a — age in years
  • activity factor — dimensionless multiplier:
    • 1.2 — Sedentary (desk job, little or 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 (hard exercise 6–7 days/week)
    • 1.9 — Extra Active (very hard daily exercise or a physical job)

Daily calorie targets adjust TDEE by ±250 or ±500 kcal/day to drive weight change. A 500 kcal/day deficit produces roughly 1 lb/week of fat loss (using the classic 3,500 kcal/lb rule), and a 250 kcal/day surplus supports a slow lean bulk of about 0.5 lb/week. In practice, metabolic adaptation slows the rate of loss after a few weeks, so re-measure every 2–4 weeks and adjust based on actual weight change. This calculator is informational only and is not a substitute for clinical judgment — consult a registered dietitian or physician before starting a very-low-calorie diet or making large changes to intake during illness, pregnancy, or chronic disease.

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