Nutrition & Fitness
Estimate your maintenance calories (TDEE), basal metabolic rate (BMR), and custom caloric targets for fat loss or muscle gain.
Understanding BMR, TDEE, and Calorie Math
Managing body weight is fundamentally governed by the energy balance equation: calories consumed versus calories expended.
1. Basal Metabolic Rate (BMR)
The energy your body expends at rest to keep your heart beating, lungs breathing, and cells regenerating. Calculated via the Mifflin-St Jeor formula.
2. Total Daily Energy (TDEE)
Your BMR multiplied by your physical activity multiplier. Eating at your TDEE keeps your body weight steady.
Read our complete calorie calculator guide
Frequently Asked Questions
What is the difference between BMR and TDEE?
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Basal Metabolic Rate (BMR) is your baseline energy burn at complete rest. Total Daily Energy Expenditure (TDEE) adds all exercise, walking, and daily activity to your BMR.
How many calories should I eat to lose 1 lb per week?
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Consuming approximately 500 calories below your TDEE each day creates a weekly deficit of 3,500 calories, which equals roughly 1 pound (0.45 kg) of fat loss.
Is any personal data stored?
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No. Calculations run strictly on your browser with complete privacy.
How to Interpret a Calorie Estimate
Enter age, sex, height, weight, and activity level using consistent units. The calculator estimates resting energy needs and then applies an activity factor to estimate daily maintenance calories. This is a planning starting point, not a measurement of metabolism. Body composition, sleep, illness, medication, training load, and the accuracy of the inputs can all change actual needs.
Formula and example
The common Mifflin-St Jeor equations estimate resting needs from weight, height, and age, with a sex-specific constant, then multiply by an activity factor. A 30-year-old person weighing 70 kg and measuring 175 cm will receive a different estimate at sedentary and very active settings. Change one input at a time and record the units so the comparison is meaningful.
Practical use
Use the maintenance estimate as a range and watch the trend over two to four weeks rather than reacting to one day. Food labels, restaurant portions, cooking oils, drinks, and weekend meals are frequent sources of undercounting. If adjusting body weight, make gradual changes and include protein, fiber, hydration, and enjoyable foods. Athletes, teenagers, pregnant people, and anyone with a medical condition should seek individualized advice.
Mistakes and limitations
Do not enter pounds where kilograms are requested, select an activity level that describes your aspiration rather than your routine, or treat the result as a diagnosis. Calories are not the only measure of nutrition quality, and the estimate cannot assess allergies or nutrient deficiencies. Recheck your inputs and consult a qualified professional when a large change is needed.
Related reading
For the mathematics and activity assumptions, read the calorie calculator guide. Pair calorie planning with the BMI calculator only as a broad screening comparison, not as a complete health assessment.
Making the estimate useful
Use a consistent weighing routine and compare weekly trends, because water, sodium, digestion, and exercise can move scale weight from one day to the next. Recalculate after a meaningful change in body weight or routine, but do not chase every fluctuation. The safest interpretation is a starting range that you test against real observations and adjust gradually with qualified guidance.
Using a Calorie Estimate Responsibly
A calorie estimate is a starting point, not a diagnosis or a prescription. The calculator uses age, sex setting, height, weight, and activity to estimate basal energy needs and daily maintenance. Your actual needs can change with training, sleep, medication, pregnancy, illness, and changes in body composition. Use a consistent method for several weeks and discuss major changes with a qualified professional.
Formula and worked example
A common resting-energy equation is Mifflin–St Jeor. For men, BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age + 5. For women, replace the final constant with −161. Convert pounds to kilograms by multiplying by 0.453592 and inches to centimeters by multiplying by 2.54. If a 30-year-old man weighs 80 kg and is 180 cm tall, the estimate is 800 + 1125 − 150 + 5 = 1,780 kcal per day before activity.
Activity Factors and Mistakes
Multiplying BMR by an activity factor estimates maintenance, but a desk job with occasional exercise should not be treated like daily hard training. Log meals honestly, use the same weighing routine, and avoid changing several variables at once. Calories are not interchangeable with nutrition quality: protein, fiber, hydration, and micronutrients still matter.
FAQs and links
Why do two calculators differ? They may use different formulas, units, or activity definitions. Should I eat exactly the displayed number? No; treat it as an estimate and observe your trend. Does age affect the result? Yes, it is part of the equation. Use the BMI calculator for a separate screening measure, and the weight converter when your scale uses another unit.
Turning an Estimate into a Plan
Use the displayed maintenance estimate as a comparison point. Record portions, drinks, cooking oils, and weekend meals because small omissions can explain a difference between a log and a scale trend. A gradual change is easier to interpret than a dramatic target. Recalculate after a meaningful change in body weight or routine, not after every single day.
Safety reminder
Children, pregnant or breastfeeding people, athletes, and anyone managing a medical condition may need a different assessment. Seek professional advice before setting a restrictive target. The calculator estimates energy, while a balanced plan also considers protein, fiber, fluids, vitamins, and personal preferences.
Tracking the Trend
Daily calorie needs naturally vary. Compare a consistent seven-day pattern, sleep, activity, and body-weight trend rather than reacting to one reading. A food scale can improve portion estimates, but labels and restaurant servings also contain uncertainty.
How to use the calorie calculator well
Use your age, height, weight, and activity level as an honest starting point rather than trying to choose the most flattering option. The result estimates maintenance calories, often called total daily energy expenditure (TDEE). It is not a medical diagnosis and it cannot account perfectly for sleep, medication, muscle mass, pregnancy, or changing training loads.
The formula behind the estimate
Many calculators first estimate basal metabolic rate (BMR) with the Mifflin-St Jeor equation. For men, BMR is 10 times weight in kilograms plus 6.25 times height in centimeters, minus 5 times age, plus 5. For women, the final constant is minus 161. TDEE is then approximately BMR multiplied by an activity factor. For example, a 30-year-old woman at 65 kg and 165 cm has a BMR near 1,370 calories; a moderately active factor of 1.55 produces roughly 2,120 maintenance calories.
Practical steps
- Measure body weight under similar conditions, preferably in the morning.
- Choose the activity level that describes your normal week, not an occasional hard workout.
- Compare the estimate with a seven-day average of your food intake and weight trend.
- Adjust gradually after two or three weeks if your goal and trend do not match.
Common mistakes and safety notes
Do not double-count exercise by selecting a high activity factor and then automatically eating back every watch calorie. Packaged-food labels and restaurant portions also introduce error. A small calorie deficit is usually easier to sustain than an aggressive restriction, while athletes may need more carbohydrate around training. Children, pregnant or breastfeeding people, and anyone managing diabetes or an eating disorder should use individualized advice from a qualified clinician.
Questions people ask
Should I eat the exact number? No. Treat it as a range and use your trend over time. Why did my estimate change? A change in weight, age, activity, or unit selection changes the equation. What should I track? Calories, protein, sleep, training, and a weekly weight average give more context than a single scale reading. For related planning, see our BMI calculator and weight converter.
Understand exactly how your daily calorie needs are calculated — the science behind BMR and TDEE, real worked examples, activity multipliers, and how to set a realistic weight goal.
What Are Calories, BMR, and TDEE?
A calorie (technically a kilocalorie, or kcal) is a unit of energy. Your body burns calories constantly — to breathe, circulate blood, maintain body temperature, and power every cellular process. Understanding three key numbers helps you plan your nutrition:
- BMR (Basal Metabolic Rate): The calories your body burns at complete rest — just to stay alive. It represents roughly 60–75% of your total energy expenditure.
- TDEE (Total Daily Energy Expenditure): Your BMR multiplied by an activity factor. This is the total number of calories you burn per day, including exercise, work, and daily movement.
- Maintenance Calories: The calorie intake where your weight stays stable — equal to your TDEE.
The Mifflin-St Jeor Equation (The Gold Standard)
The most widely validated BMR formula for the general population, used by our calculator:
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
TDEE:
TDEE = BMR × Activity Multiplier
Step-by-Step Worked Examples
Example 1: 35-Year-Old Man, Moderately Active
Weight: 80 kg | Height: 178 cm | Age: 35 | Activity: Moderate (×1.55)
- BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5
- BMR = 800 + 1,112.5 − 175 + 5 = 1,742.5 kcal/day
- TDEE = 1,742.5 × 1.55 = 2,700 kcal/day
- For weight loss (−500 kcal): 2,200 kcal/day
- For weight gain (+300 kcal): 3,000 kcal/day
Example 2: 28-Year-Old Woman, Lightly Active
Weight: 62 kg | Height: 165 cm | Age: 28 | Activity: Light (×1.375)
- BMR = (10 × 62) + (6.25 × 165) − (5 × 28) − 161
- BMR = 620 + 1,031.25 − 140 − 161 = 1,350.25 kcal/day
- TDEE = 1,350.25 × 1.375 = 1,857 kcal/day
- For gradual weight loss (−300 kcal): 1,557 kcal/day
Activity Level Multipliers Reference Table
Choose the multiplier that honestly reflects your average week — not your busiest or most sedentary week:
| Activity Level |
Multiplier |
Description |
| Sedentary | ×1.2 | Desk job, little or no exercise |
| Lightly Active | ×1.375 | Light exercise 1–3 days/week |
| Moderately Active | ×1.55 | Moderate exercise 3–5 days/week |
| Very Active | ×1.725 | Hard exercise 6–7 days/week |
| Extra Active | ×1.9 | Physical job + hard training, or twice-daily training |
Understanding Your Macronutrient Split
Once you know your TDEE, you can divide your calories into macronutrients. Each gram of macronutrient provides a fixed amount of energy:
| Macronutrient |
kcal/gram |
General Recommendation |
Example (2,500 kcal diet) |
| Protein | 4 kcal/g | 25–35% of calories | ~156–219 g |
| Carbohydrates | 4 kcal/g | 40–55% of calories | ~250–344 g |
| Fat | 9 kcal/g | 20–35% of calories | ~56–97 g |
How to Set a Realistic Calorie Goal
- For weight loss: Create a deficit of 300–500 kcal/day below TDEE. This produces roughly 0.3–0.5 kg (0.6–1 lb) of fat loss per week. Deficits larger than 750 kcal/day risk muscle loss and metabolic adaptation.
- For weight gain (muscle): Add 200–300 kcal/day above TDEE to minimize fat gain while supporting muscle protein synthesis. Pair with resistance training.
- For maintenance: Eat at TDEE. Weigh yourself 3× per week and track the 7-day average to account for natural daily fluctuations (water, food volume, hormones).
- Recalculate regularly: As your weight changes, your BMR changes. Recalculate your TDEE every 5–10 kg of weight change or if your activity level shifts significantly.
- Never go below 1,200 kcal (women) or 1,500 kcal (men) without medical supervision. Very low calorie diets risk nutrient deficiencies, muscle loss, and hormonal disruption.
What does the calorie calculator estimate?
It estimates daily energy needs from the body and activity inputs you provide.
Why can two people get different results?
Energy needs vary with body size, age, activity, goals, and individual physiology.
Is the result exact?
No. It is an estimate intended for planning, not a laboratory measurement.
How should I use the estimate?
Use it as a starting point and adjust based on goals, real-world results, and appropriate professional guidance.
