Calorie Calculator
Calculate your daily calorie needs using Mifflin-St Jeor or Katch-McArdle. Supports metric and imperial units, gender-aware calorie floors, goal-specific macro ratios, and a full macronutrient breakdown.
Key Features
- •Mifflin–St Jeor formula (default — most validated for general population)
- •Katch–McArdle formula (auto-activates when body fat % is provided — gender-neutral, uses lean mass)
- •Full metric support: cm height input with independent kg/lbs weight toggle
- •Full imperial support: ft+in height inputs with independent kg/lbs weight toggle
- •Gender-aware minimum calorie floors: 1,500 kcal for men, 1,200 kcal for women
- •5 activity levels with plain-language descriptions
- •5 goal presets: Lose Weight, Lose Fast, Maintain, Gain Muscle, Lean Bulk
- •Goal-specific macro ratios: protein/carb/fat percentages adjust per goal
- •Macronutrient breakdown: grams, kilocalories, and percentage for protein, carbs, and fat
- •Visual macro bar showing proportional split at a glance
- •TDEE surplus/deficit delta displayed on results (e.g. −500 from TDEE)
- •Formula transparency: results note which BMR equation was used and why
About Calorie Calculator
Whether you want to lose fat, build muscle, or maintain your current weight, understanding your Total Daily Energy Expenditure (TDEE) is the foundation of success. Our Calorie Calculator uses the Mifflin-St Jeor Equation—widely considered the most accurate BMR formula for the general population—or the Katch-McArdle formula when body fat percentage is provided. Both metric (kg/cm) and imperial (lbs/ft+in) inputs are fully supported.
The Science of Energy Balance
Weight change is governed by the laws of thermodynamics:
- Calorie Deficit (Eat less than TDEE): Weight loss occurs. A deficit of 500 calories per day results in approximately 1 lb (0.45 kg) of fat loss per week.
- Calorie Surplus (Eat more than TDEE): Weight gain occurs. A surplus of 500 calories per day results in approximately 1 lb of weight gain per week (some may be muscle if combined with resistance training).
- Maintenance (Eat equal to TDEE): Weight remains stable.
Step 1: Calculate Your BMR (Basal Metabolic Rate)
BMR is the number of calories your body burns at complete rest to maintain vital functions: breathing, circulation, cell production, and temperature regulation. It accounts for 60-75% of your daily calories burned.
Mifflin–St Jeor formula (default — best for general population):
- For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Katch–McArdle formula (activated when body fat % is provided — more accurate for lean individuals):
- BMR = 370 + (21.6 × Lean Body Mass in kg)
- Lean Body Mass = Weight × (1 − Body Fat% / 100)
- This formula is gender-neutral and accounts for individual body composition, making it the most precise option for athletes, bodybuilders, and anyone who knows their body fat percentage.
Example: A 30-year-old woman, 165 cm (5'5"), 65 kg (143 lbs):
BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031.25 − 150 − 161 = 1,370 calories/day
Step 2: Apply Activity Multipliers to Find TDEE
Your TDEE = BMR × Activity Factor. Choose the factor that best represents your typical week:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Light | Light exercise 1–3 days/week | 1.375 |
| Moderate | Moderate exercise 3–5 days/week | 1.55 |
| Very Active | Hard exercise 6–7 days/week | 1.725 |
| Extreme | Physical job + intense daily training | 1.9 |
For the woman above (BMR 1,370), moderately active (gym 4 days/week): TDEE = 1,370 × 1.55 = 2,124 calories/day to maintain weight.
Step 3: Set Your Goal
The calculator adjusts both calorie target and macro ratios per goal:
| Goal | Calorie Adjustment | Protein | Carbs | Fat |
|---|---|---|---|---|
| Lose Weight | −500 kcal from TDEE | 35% | 40% | 25% |
| Lose Fast | −750 kcal from TDEE | 40% | 35% | 25% |
| Maintain | TDEE | 25% | 50% | 25% |
| Gain Muscle | +300 kcal above TDEE | 30% | 50% | 20% |
| Lean Bulk | +500 kcal above TDEE | 30% | 50% | 20% |
Gender-aware minimum calorie floors are enforced:
- Women: 1,200 kcal/day minimum
- Men: 1,500 kcal/day minimum
Going below these thresholds makes it difficult to meet micronutrient needs (iron, calcium, B vitamins) and can cause muscle loss, fatigue, hair loss, and hormonal disruption.
Macronutrient Breakdown
Calories come from three macronutrients, each with a caloric density:
- Protein: 4 kcal per gram (preserves muscle mass, increases satiety)
- Carbohydrates: 4 kcal per gram (primary energy source, fuels training)
- Fat: 9 kcal per gram (supports hormone function, fat-soluble vitamins)
Macro ratios in this calculator shift based on your goal. Higher-deficit goals increase protein to protect lean mass while reducing carbs. Surplus goals maintain higher carbs to fuel training and recovery. Each result shows grams, calories, and percentage per macro.
Practical Example: Weight Loss Plan
A 35-year-old man, 180 lbs (81.6 kg), 5'10" (178 cm), lightly active, wants to lose 1 lb/week:
- BMR (Mifflin–St Jeor): (10 × 81.6) + (6.25 × 178) − (5 × 35) + 5 = 1,759 kcal
- TDEE (lightly active × 1.375): 1,759 × 1.375 = 2,419 kcal
- Target (−500 deficit): 1,919 kcal/day (above 1,500 kcal male floor ✓)
- Protein (35%): 1,919 × 0.35 ÷ 4 = 168 g
- Carbs (40%): 1,919 × 0.40 ÷ 4 = 192 g
- Fat (25%): 1,919 × 0.25 ÷ 9 = 53 g
Beyond Calories: Food Quality Matters
While calorie math governs weight change, food quality determines health outcomes. 1,500 kcal of whole foods produces better results than the same calories from processed sources. Whole foods provide essential micronutrients, increase satiety through fiber and protein, stabilize blood sugar, and support gut microbiome diversity.
FAQ: Calorie Calculator
Why am I not losing weight even though I'm eating at a deficit?
Potential reasons: (1) Underestimating portion sizes — use a food scale, (2) Liquid calories from coffee drinks, alcohol, or juice not tracked, (3) Adaptive thermogenesis — metabolism slows with weight loss, so recalculate BMR every 5–10 lbs, (4) Water retention from high sodium or hormonal cycles.
Do I need to eat back exercise calories?
For general weight loss, no. Fitness trackers often overestimate calorie burn by 20–50%. For intense training (marathon prep, CrossFit), prioritize hunger signals over numbers.
What's the minimum safe calorie intake?
Women: 1,200 kcal; Men: 1,500 kcal. This calculator enforces these floors automatically. Below these levels it becomes difficult to meet protein, iron, calcium, and B-vitamin requirements.
Which formula should I use — Mifflin–St Jeor or Katch–McArdle?
Use Mifflin–St Jeor if you don't know your body fat percentage — it's accurate within ±10–15% for most people. Use Katch–McArdle if you've had a DEXA scan, hydrostatic weighing, or reliable body fat measurement — it removes gender from the equation and focuses purely on lean mass, making it more precise for lean or muscular individuals.
How do I use imperial units?
Select the Imperial tab and enter height as feet and inches separately (e.g., 5 ft 9 in), plus weight in pounds. The calculator converts to metric internally for all formulas and then displays results in your chosen unit system.
Should I recalculate my calories as I lose weight?
Yes. As your body weight changes, your BMR and TDEE change too. Recalculate every 5–10 lbs of weight change to keep your target accurate.
Calorie Calculator is optimized for fast browser-based use, so you can test multiple scenarios in seconds.
Formula & Logic
- 01BMR (Mifflin–St Jeor, default): Men: (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: (10 × kg) + (6.25 × cm) − (5 × age) − 161.
- 02BMR (Katch–McArdle, activated when body fat % > 0): 370 + (21.6 × LBM). LBM = weight × (1 − BF%/100). Gender-neutral.
- 03TDEE = BMR × Activity Factor (1.2 sedentary → 1.9 extreme).
- 04Calorie targets: Lose −500, Lose Fast −750, Maintain 0, Gain +300, Lean Bulk +500 relative to TDEE.
- 05Minimum calorie floors enforced per gender: 1,500 kcal (men), 1,200 kcal (women). Applied after deficit calculation.
- 06Macro ratios per goal — Lose: P35/C40/F25. Lose Fast: P40/C35/F25. Maintain: P25/C50/F25. Gain: P30/C50/F20. Lean Bulk: P30/C50/F20.
- 07Protein calories ÷ 4 = grams. Carb calories ÷ 4 = grams. Fat calories ÷ 9 = grams.
- 08Imperial conversion: lbs × 0.453592 = kg. (ft × 12 + in) × 2.54 = cm. Weight unit (kg/lbs) is a shared toggle independent of the height unit tab — applies to both metric and imperial height inputs.
Practical Examples
- 01Baseline check: Use realistic inputs in Calorie Calculator to generate a first-pass estimate.
- 02Sensitivity check: Change one key input at a time to compare how the output shifts.
- 03Decision check: Save two or more scenarios and use the differences to choose the better option.
Important Limitations
- •Results depend on the accuracy of your inputs.
- •Displayed values may be rounded for readability.
- •Health-related outputs are educational estimates and should not replace medical advice.
Frequently Asked Questions
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