BMR / TDEE Calculator

What is TDEE?

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, combining your basal metabolic rate (BMR) with the energy used for physical activity and digestion. Knowing your TDEE helps you manage weight: eat fewer calories to lose weight, more to gain, or match it to maintain.

TDEE is composed of three parts: BMR (60-70% of TDEE, energy for basic life functions), the thermic effect of food (about 10%, energy to digest and absorb food), and physical activity (20-30%, the most variable component). The activity level multiplier accounts for exercise and daily movement patterns.

The four components of TDEE

TDEE is not a single number from a single process — it is the sum of four distinct energy pools, each of which varies independently.

• Basal Metabolic Rate (BMR): the largest share — typically 60–70% of TDEE — is the energy your body consumes at complete rest to sustain vital functions: breathing, circulation, cell repair, temperature regulation, and organ operation. BMR is driven mostly by lean mass, which is why two people of the same weight but different body compositions can have very different BMRs.
• Thermic Effect of Food (TEF): roughly 8–10% of TDEE is spent digesting, absorbing, and storing the macronutrients you eat. Protein has the highest thermic cost (20–30% of its own calories), making it the most metabolically expensive macronutrient. Carbohydrates cost about 5–10%, and fat only 0–3%.
• Non-Exercise Activity Thermogenesis (NEAT): this covers all movement that is not formal exercise — walking to the kitchen, typing, fidgeting, standing at a desk. NEAT is the most variable component across individuals (ranging from around 200 to over 1,000 kcal/day) and is a major reason why two people eating the same diet can have different weight outcomes.
• Exercise Activity Thermogenesis (EAT): the calories burned during intentional, structured physical activity such as running, cycling, or strength training. This component is the one most directly within your control.

The Mifflin-St Jeor equation

This calculator uses the Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition in 1990 and consistently validated as the most accurate predictive formula for resting energy expenditure in healthy adults. The formulas are:

• Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
• Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

The only difference between the two formulas is the final constant: +5 for men and −161 for women. This offset reflects average differences in lean body mass and hormonal baseline between sexes. TDEE is then calculated by multiplying the BMR by an activity factor: TDEE = BMR × activity multiplier.

Activity level multipliers

• Sedentary (office job, little exercise): BMR x 1.2.
• Lightly active (light exercise 1-3 days/week): BMR x 1.375.
• Moderately active (moderate exercise 3-5 days/week): BMR x 1.55.
• Very active (hard exercise 6-7 days/week): BMR x 1.725.
• Extremely active (physical job + hard exercise): BMR x 1.9.

Worked example

Consider a 30-year-old man who weighs 80 kg and is 178 cm tall, with a moderately active lifestyle (exercise 3–5 days per week).

Step 1 — calculate BMR: (10 × 80) + (6.25 × 178) − (5 × 30) + 5 = 800 + 1112.5 − 150 + 5 = 1,767.5 kcal/day.

Step 2 — multiply by the activity factor: 1,767.5 × 1.55 = 2,740 kcal/day (rounded). This is his estimated TDEE — the number of calories he needs to maintain his current weight.

For a 35-year-old woman, 65 kg, 165 cm, lightly active (1–3 days/week exercise): BMR = (10 × 65) + (6.25 × 165) − (5 × 35) − 161 = 650 + 1031.25 − 175 − 161 = 1,345.25 kcal/day. TDEE = 1,345.25 × 1.375 = 1,850 kcal/day.

Applying TDEE to fat loss, maintenance, and muscle gain

Once you know your TDEE, adjusting calorie intake becomes straightforward arithmetic. The key principle is that 1 kg of body fat stores approximately 7,700 kcal, meaning a daily deficit of 500 kcal produces roughly 0.45 kg (1 lb) of fat loss per week.

• Fat loss: aim for a daily calorie intake of 10–20% below your TDEE. For most people this works out to a deficit of 250–500 kcal/day. A 10% deficit (sometimes called a mild cut) is sustainable for months and preserves more muscle. A 20% deficit accelerates progress but requires careful protein intake (target 1.6–2.2 g per kg of body weight) to limit muscle loss.
• Maintenance: eat at TDEE. This is the target during a diet break, a deload week, or when body composition is already at goal. Because TDEE is an estimate, fine-tune by tracking weight weekly and adjusting intake by 100–150 kcal if weight trends up or down.
• Muscle gain (lean bulk): eat 100–300 kcal above TDEE. A larger surplus accelerates fat gain without meaningfully increasing the rate of muscle synthesis, since muscle protein accretion is limited by the body's anabolic ceiling (roughly 0.5–1 kg of muscle per month for most trained individuals).

Using TDEE for weight management

To lose weight, eat 300-500 calories below your TDEE (a moderate deficit that preserves muscle mass). To gain weight, eat 250-500 calories above TDEE. A 500-calorie daily deficit equals approximately 0.45 kg (1 pound) of weight loss per week. Extreme deficits (over 1,000 calories below TDEE) are unsustainable and can cause muscle loss, metabolic slowdown, and nutritional deficiencies.

Accuracy and limitations

Predictive equations like Mifflin-St Jeor estimate TDEE within approximately ±10–15% of a person's true expenditure for most adults. That margin is wider for people with very high or low body fat percentages (the formula relies on total weight, not lean mass), for older adults (after 60, metabolic rate can fall faster than the age term predicts), and for people with certain medical conditions affecting thyroid function or hormonal balance.

The activity multiplier introduces further uncertainty. Most people tend to overestimate how active they are — selecting 'very active' when 'moderately active' better matches their week. In practice it is safer to start with the multiplier one step below what feels right, then adjust upward if weight drops faster than expected.

Common mistakes

• Overestimating activity level: the most frequent error. An office worker who goes to the gym three times a week is moderately active at most — not very active. When in doubt, choose the lower multiplier.
• Eating below BMR: BMR represents the minimum calories needed to sustain organ function. Sustained intake below BMR triggers adaptive thermogenesis — the body slows metabolism, breaks down muscle for energy, and makes fat loss progressively harder.
• Not adjusting TDEE over time: as body weight changes, BMR changes too. Recalculate every 4–6 weeks or whenever weight shifts by 3–5 kg.
• Ignoring NEAT: adding a gym session does not offset an otherwise sedentary day. Small increases in daily movement — a 20-minute walk, taking stairs — can raise NEAT by 200–300 kcal/day with far less effort.

How to use this tool

Enter your age, gender, weight, height, and activity level. The tool calculates your BMR using established formulas (Mifflin-St Jeor or Harris-Benedict) and multiplies by an activity factor to estimate your TDEE. Results show daily calorie targets for maintenance, weight loss (deficit), and weight gain (surplus).

Frequently asked questions

How accurate is a TDEE calculator?

TDEE calculations are estimates, typically within 10-15% of actual expenditure. Individual variations in metabolism, body composition, NEAT (non-exercise activity thermogenesis like fidgeting), and genetics can cause significant differences. Use the calculated TDEE as a starting point, then adjust based on real-world results over 2-4 weeks.

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep vital organs functioning (breathing, circulation, cell production). TDEE includes BMR plus all additional energy expenditure from physical activity, digestion, and daily movement. BMR is typically 60-70% of TDEE. You should never eat below your BMR.

Should I eat more on exercise days?

Yes, many people find it practical to cycle calories — eating closer to (or slightly above) TDEE on training days and at a small deficit on rest days. This keeps net weekly intake on target while ensuring muscle glycogen is replenished before workouts. The total weekly calorie balance matters more than any single day.

Does TDEE change as I age?

Yes. BMR — and therefore TDEE — declines gradually with age, primarily because lean muscle mass tends to decrease after the mid-20s unless actively maintained through resistance training. The Mifflin-St Jeor formula captures the average age-related decline through the age term (−5 × age), but individual variation is large. Regular strength training and adequate protein intake are the most effective strategies to preserve metabolic rate as you get older.

The information on this page is provided for general educational purposes only and is not a substitute for professional medical or dietary advice. Consult a qualified healthcare provider before making significant changes to your diet or exercise programme, particularly if you have an existing medical condition.