The number of calories you should eat depends almost entirely on one thing: how many calories you burn in a day. That number is called your TDEE — Total Daily Energy Expenditure.
Get that number right, and everything else — weight loss, maintenance, muscle gain — follows from a simple formula. This post explains how TDEE is calculated, what BMR is, how activity level factors in, and what your actual calorie target should be. If you haven't checked your BMI yet, that's a useful first step for understanding where you're starting from.
What is TDEE?
TDEE is the total number of calories your body burns in a 24-hour period, including everything: the calories burned keeping your organs running while you sleep, the calories burned walking to your car, the calories burned in a gym session.
To eat at maintenance (not gain or lose weight), your calorie intake needs to match your TDEE. To lose weight, you need to eat less. To gain weight, you need to eat more.
The average TDEE for adult women is roughly 1,600–2,400 calories per day. For men, it's typically 2,000–3,000. But "average" doesn't tell you what YOUR number is — your height, weight, age, and especially your activity level matter significantly.
Step 1: Calculate your BMR
BMR — Basal Metabolic Rate — is the number of calories your body needs just to exist. No movement, no digestion, just the baseline functions: heart beating, lungs breathing, cells regenerating.
The most accurate commonly-used formula is Mifflin-St Jeor (developed 1990, validated in multiple studies):
BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women:
BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
Example — 35-year-old woman, 65 kg, 165 cm:
BMR = (10 × 65) + (6.25 × 165) − (5 × 35) − 161
= 650 + 1,031 − 175 − 161 = 1,345 calories/day
Example — 28-year-old man, 80 kg, 178 cm:
BMR = (10 × 80) + (6.25 × 178) − (5 × 28) + 5
= 800 + 1,112 − 140 + 5 = 1,777 calories/day
BMR is not your calorie target — it's just your resting baseline. Most people burn significantly more than their BMR when you account for daily movement.
Step 2: Multiply by your activity level
Your TDEE is calculated by multiplying your BMR by an activity multiplier. This accounts for how much you move beyond your baseline metabolic functions.
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | × 1.2 |
| Lightly active | Light exercise 1–3 days/week | × 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | × 1.55 |
| Very active | Hard exercise 6–7 days/week | × 1.725 |
| Extra active | Very hard exercise, physical job | × 1.9 |
Continuing the examples above:
35-year-old woman, lightly active (BMR 1,345):
TDEE = 1,345 × 1.375 = ~1,850 calories/day
28-year-old man, moderately active (BMR 1,777):
TDEE = 1,777 × 1.55 = ~2,754 calories/day
These are maintenance calories — eat this much, and your weight stays roughly stable.
Setting your calorie target
Once you have your TDEE, adjust based on your goal:
- Weight loss: Eat 300–500 calories below TDEE. A 500-calorie daily deficit adds up to roughly 1 pound per week (since 3,500 calories ≈ 1 lb of fat). A 250-calorie deficit gives you about 0.5 lbs/week — slower but more sustainable.
- Maintenance: Eat at TDEE. This keeps your weight stable while giving you the energy your body needs.
- Muscle gain: Eat 200–500 calories above TDEE. More than that and a larger proportion of the gain will be fat rather than muscle.
Important floor: Going below 1,200 calories per day (women) or 1,500 calories per day (men) is not recommended without medical supervision. Very low intakes compromise muscle retention, nutrient absorption, hormonal function, and metabolic rate over time.
Why these numbers are estimates
TDEE calculators give you a useful starting estimate, not a precise measurement. Several factors introduce variation:
- Activity multipliers are approximations. "Moderately active" is subjective. The multiplier assumes an average pattern, which won't perfectly match your actual week.
- Metabolic adaptation. When you reduce calories significantly, your body responds by lowering TDEE — burning less at rest. This is the main reason weight loss slows after the first few weeks.
- Calorie labels are imprecise. FDA regulations allow up to 20% error on nutrition labels. A food labeled 100 calories could be anywhere from 80–120.
- Individual variation. Two people with identical stats can have meaningfully different metabolic rates due to genetics, gut microbiome, and other factors.
The practical implication: use your TDEE as a starting point. Track your weight over 2–3 weeks. If you're not losing when you expected to, reduce by another 100–200 calories and reassess.
The protein piece
Calorie amount matters most for weight change. Calorie source matters most for body composition. If you're in a calorie deficit and don't eat enough protein, you'll lose both fat and muscle. If you eat enough protein, you preserve muscle while losing fat.
A commonly cited target: 0.7–1g of protein per pound of body weight (or 1.6–2.2g per kg). This is especially important during weight loss phases.
Calculate your exact TDEE and daily calorie target
Open TDEE Calculator →Also try the Calorie Calculator for a quick estimate, or the BMR Calculator if you want to see just your resting metabolic rate.