How Many Calories Should You Eat? TDEE Explained

Basal Metabolic Rate (BMR) is the calories your body needs at complete rest — essentially the cost of staying alive. The most widely validated formula for most adults is the Mifflin-St Jeor equation:

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

Worked example: A 30-year-old woman, 165 cm tall, weighing 70 kg:
(10 × 70) + (6.25 × 165) − (5 × 30) − 161 = 700 + 1031.25 − 150 − 161 = 1,420 kcal/day

The older Harris-Benedict formula is still in common use and gives similar results. Both are estimates — your true BMR can vary by ±10% depending on body composition, genetics, and hormonal status. Lean mass burns more than fat mass, which is why two people with identical weight can have very different BMRs.

TDEE = BMR × Activity Multiplier. This multiplier accounts for all movement, not just formal exercise. The standard scale used in most research:

Continuing the example above — the same woman works a desk job but hits the gym three times a week (lightly active, 1.375):
1,420 × 1.375 = ~1,953 kcal/day TDEE

Most people underestimate sedentary time and overestimate exercise intensity. When in doubt, round down one level and adjust based on real-world results over 2–3 weeks.

One pound of body fat contains roughly 3,500 kcal. A deficit of 500 kcal/day therefore produces approximately 1 lb of loss per week — a figure that holds up reasonably well in controlled studies for most people in the first several weeks of a diet.

Practical sizing guidelines:

• Moderate deficit (15–20% below TDEE): Best for most people. Preserves muscle, sustainable for months. At 1,953 kcal TDEE, this means eating 1,560–1,660 kcal/day — roughly 300–400 kcal below maintenance.
• Aggressive deficit (25–30% below TDEE): Accelerates loss but increases muscle loss risk and hunger. Use only with adequate protein (at least 1.6 g/kg of body weight) and no longer than 8–12 weeks without a diet break.
• Never below BMR without medical supervision. Eating below 1,200 kcal/day (women) or 1,500 kcal/day (men) almost always causes muscle wasting and micronutrient shortfalls regardless of what the math says.

Protein intake is the most important diet variable when in a deficit. A target of 2.0–2.4 g per kg of body weight is well-supported by meta-analyses for preserving lean mass during caloric restriction.

Muscle tissue can only be synthesized so fast. Research on trained individuals suggests a natural rate of roughly 0.5–1 lb of lean mass per month once past the beginner stage. Eating far above maintenance does not speed this up — it just adds more fat.

• Lean bulk (5–10% above TDEE): ~100–200 extra kcal/day. Slow fat gain, best for intermediate and advanced lifters. At 1,953 TDEE, target 2,050–2,150 kcal/day.
• Standard bulk (15–20% above TDEE): Faster scale movement, but expect roughly equal fat and muscle gain. Useful for beginners who gain muscle quickly.

Tracking body weight weekly (same conditions: morning, post-bathroom) and averaging over a month gives a reliable signal of whether you are in the right zone.

Weight loss plateaus are physiologically real, not a myth. As body weight drops, BMR falls because there is simply less mass to maintain. A 10% loss in body weight typically reduces TDEE by 5–8% — sometimes more due to adaptive thermogenesis, where the body down-regulates non-essential energy expenditure.

When the scale has not moved for two or more full weeks (ruling out water retention from sodium, hormonal cycles, or new training), you have genuinely hit a plateau. The response should be one of three things:

1. Reduce calories by 100–150 kcal/day. Small adjustments are usually enough and less disruptive than large cuts.
2. Add 20–30 minutes of low-intensity cardio on rest days. Burns extra calories without adding meaningful recovery debt.
3. Take a 1–2 week diet break at maintenance calories. Partially reverses adaptive thermogenesis and often improves adherence in the following phase. Evidence for this approach has grown substantially since 2018.

Re-estimate your TDEE every 5–7 kg of weight change. The number you calculated at 80 kg is meaningfully different from your TDEE at 72 kg. Treating TDEE as a fixed target instead of a moving one is one of the most common reasons long-term diets fail.

The framework in four steps:

1. Calculate BMR using Mifflin-St Jeor.
2. Multiply by your honest activity level to get TDEE.
3. Set a deficit (fat loss) or surplus (muscle gain) as a percentage of TDEE — not a flat number pulled from a generic chart.
4. Track results for 2–3 weeks, then adjust by 100–200 kcal if the trend is not matching the goal.

No calculator — including this one — can account for every individual variable. Stress hormones, sleep quality, gut microbiome composition, and medication all influence energy balance in ways that cannot be measured from height, weight, and age alone. Use the number as a starting hypothesis, not a law. Your body's response over time is the most accurate data you have.