What is TDEE, and how do I actually calculate mine?
TDEE — Total Daily Energy Expenditure — is the total calories your body burns in a day. It's the single most useful number in any kind of intentional eating: gain, lose, or maintain.
The components of TDEE
Your daily calorie burn breaks into four chunks. Different sources use different abbreviations; the chunks are the same.
- BMR (Basal Metabolic Rate) — calories burned at complete rest just to stay alive. Heart beating, lungs breathing, brain running, body temperature held at 37°C. This is the biggest piece, usually 60-70% of TDEE.
- TEF (Thermic Effect of Food) — calories burned digesting and processing what you eat. About 10% of TDEE. Higher for protein-heavy diets (protein costs more to digest).
- EAT (Exercise Activity Thermogenesis) — calories from intentional exercise. Highly variable: 0 for the sedentary, 300-800 for typical recreational athletes.
- NEAT (Non-Exercise Activity Thermogenesis) — everything else. Walking to the kitchen, fidgeting, standing instead of sitting, taking the stairs. Surprisingly large: can vary by 1,000+ calories per day between people of the same size.
Step 1: calculate BMR
The Mifflin-St Jeor equation, published in 1990, is the most accurate of the popular formulas for a typical adult. It's what nutritionists default to.
For men:
For women:
A 30-year-old man, 180 cm, 80 kg: BMR = 800 + 1125 − 150 + 5 = 1,780 cal/day. A 30-year-old woman, 165 cm, 65 kg: BMR = 650 + 1031.25 − 150 − 161 = 1,370 cal/day.
If you know your body fat percentage, the Katch-McArdle formula is more accurate: BMR = 370 + 21.6 × lean body mass (kg). It controls for the fact that muscle burns more at rest than fat. For most people, the difference vs Mifflin-St Jeor is small.
Step 2: multiply by an activity factor
Once you have BMR, the simplest way to estimate TDEE is to multiply by an activity factor that captures EAT + NEAT + TEF. The widely-used factors:
- 1.2 — sedentary. Desk job, little/no exercise, drive everywhere.
- 1.375 — lightly active. Office work, walking some, exercise 1-3 days/week.
- 1.55 — moderately active. On your feet some, exercise 3-5 days/week.
- 1.725 — very active. Physical job or daily intense training.
- 1.9 — extremely active. Athlete with two-a-day training, or hard physical labor.
Our 30-year-old man with a desk job and three gym sessions a week: TDEE = 1,780 × 1.375 = 2,448 cal/day.
The dirty secret about activity factors
Most people overestimate. Specifically: "moderately active" is what the gym promotes; it's not what your day actually looks like. If you sit at a desk for 8 hours, drive home, watch TV, and go to the gym 3x for an hour, you're "lightly active" by metabolism math — even if subjectively you "exercise a lot."
A more honest approach: start with "lightly active" (1.375) as your default, and bump up only if your job has you on your feet most of the day. The gym counts less than people think, because an hour of moderate cardio is maybe 300-400 calories — about 15% of BMR.
Skip the math
The TDEE calculator takes your stats and gives you all five activity-level estimates plus the macro split. Updates as you type.
How to use TDEE
The point of knowing your TDEE is calorie-balance arithmetic:
- Maintain weight. Eat about TDEE.
- Lose weight. Eat TDEE minus 300-500 cal/day. Slower deficits = less muscle loss + easier compliance. Anything beyond 1,000-cal deficit is unsustainable for most people.
- Gain weight (or muscle). Eat TDEE plus 200-500 cal/day. Faster surplus = more fat alongside muscle.
A 500-calorie deficit per day, sustained for a month, is about 4 pounds. Sustained for 6 months, about 24 pounds. The math isn't faster than that — anyone promising "lose 20 lbs in 30 days" is selling unsustainable extremes or untruths.
Why your TDEE estimate will be a little wrong
The formulas are population averages. Your actual TDEE varies from the prediction by ±200 calories. Reasons:
- Body composition (muscle vs fat ratio)
- Genetics — some people just have faster or slower metabolism
- NEAT — varies wildly and is hard to estimate
- Adaptive thermogenesis — metabolism slows when you cut calories long enough
- Whether you're growing/losing/holding (these change your TDEE)
The right approach: calculate, eat at the estimate for 2-3 weeks, and adjust based on what your body actually does. If you're not losing weight at TDEE - 500, your real TDEE is less than estimated. Drop 100-200 cal more, try again. Treat the calculation as the starting point of a feedback loop, not a destination.
The TL;DR
TDEE = BMR × activity factor, give or take. Use Mifflin-St Jeor for BMR, pick "lightly" or "moderately active" honestly, and treat the result as a hypothesis to test. Sustainable changes (gain or loss) happen at ±300-500 calories from TDEE. Anything more extreme is either short-term tactical or unhealthy.