TDEE, BMR, and Maintenance Calories: The Numbers That Actually Run Your Diet

You want to lose weight, gain weight, or just understand your nutrition. Every serious calorie calculator returns two or three numbers — BMR, TDEE, and maintenance calories. Knowing what each means and how they relate turns calorie math from guessing into arithmetic.

BMR: Basal Metabolic Rate

BMR is the calories your body burns at complete rest — if you lay in bed all day, not sleeping but not moving, in a thermo-neutral room (around 70°F). It covers:

• Heart and lung function
• Brain activity
• Kidney and liver function
• Cellular repair and maintenance
• Basic body temperature regulation

Typical BMR ranges: women 1,200-1,600 kcal/day, men 1,500-2,000 kcal/day. BMR is driven primarily by lean body mass — more muscle means a higher BMR because muscle tissue is metabolically expensive to maintain at rest.

Common BMR formulas:

• Mifflin-St Jeor (most accurate for most people):
  Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
  Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
• Harris-Benedict (older, slightly less accurate on modern populations)
• Katch-McArdle (most accurate if you know your body fat percentage): BMR = 370 + 21.6 × lean body mass (kg)

A 35-year-old woman, 5’6”, 150 lb (68 kg, 168 cm): BMR ≈ 10(68) + 6.25(168) − 5(35) − 161 = 680 + 1050 − 175 − 161 = 1,394 kcal/day.

TDEE: Total Daily Energy Expenditure

TDEE is BMR plus everything else you do in a day. It breaks down roughly as:

• BMR — 60-70% of total, as above
• TEF (Thermic Effect of Food) — 8-15% of total. Digesting food burns calories. Protein has the highest thermic effect (20-30% of its calories are burned in digestion), carbs (5-10%), fat (0-3%).
• NEAT (Non-Exercise Activity Thermogenesis) — 15-30% of total. Walking around the office, fidgeting, typing, standing, talking with hands. NEAT varies enormously between individuals and is the hidden reason identical-BMR people can have 500+ kcal differences in daily burn.
• EAT (Exercise Activity Thermogenesis) — 5-15% of total for most people; can be 20%+ for serious athletes. This is deliberate exercise.

The shortcut: TDEE = BMR × activity multiplier.

Most people overestimate their activity level. A desk worker who goes to the gym three times a week is usually “lightly active” — not “moderately.” The multiplier should reflect your whole day, not just the hour in the gym.

Our 1,394-BMR example, moderately active: TDEE = 1,394 × 1.55 = 2,161 kcal/day.

Maintenance calories

Maintenance calories equal your TDEE. Eat TDEE and your weight stays stable over time. Eat 500 calories less per day than TDEE and you lose about 1 pound per week. Eat 500 calories more and you gain about 1 pound per week. This is because 1 pound of body fat stores about 3,500 kcal — so a 500 kcal/day deficit × 7 days = 3,500 kcal = 1 lb.

The 3,500 kcal number is a rough average and overstates the arithmetic for long-term weight loss. As you lose weight, your BMR drops (smaller body = less maintenance energy), so the same deficit produces smaller losses over time. A 20-pound loss at 500 kcal/day deficit rarely takes only 20 weeks; it is usually 25-30 weeks because of metabolic adaptation.

Putting it together: three scenarios

Back to our 1,394-BMR woman with TDEE 2,161 kcal/day:

Weight loss (1 lb/week)

Target intake: 2,161 − 500 = 1,661 kcal/day. Moderate deficit. Sustainable for most people. Faster loss requires larger deficit (not recommended — 500-750 is the sweet spot for most).

Weight maintenance

Target intake: 2,161 kcal/day. Simple in theory, hard in practice because intake varies daily. Track a weekly average, not a daily number.

Weight gain (0.5 lb/week)

Target intake: 2,161 + 250 = 2,411 kcal/day. Slow gain is ideal for adding muscle (faster gain is mostly fat). Pair with resistance training.

Why your actual burn does not match the calculator

Estimates are estimates. Real TDEE can differ by 10-20% from the formula prediction because of:

• Genetic variation in metabolic rate (up to ±15%)
• Thyroid function — hypothyroid can drop BMR 10-20%
• NEAT variance — some people fidget 400 kcal/day worth, others 50
• Sleep quality — chronic sleep deprivation lowers metabolic rate
• Medication effects — some antidepressants, beta blockers, and others
• Recent dieting history — post-diet metabolic adaptation can linger for months
• Body composition at the same weight (more muscle = higher burn)

Use the calculated TDEE as a starting point. Track food intake and weight for 2-3 weeks. If weight is stable at 2,200 kcal/day, your actual TDEE is 2,200 — not the formula’s 2,161. Adjust from there.

Why calorie counts on food labels also lie slightly

The FDA allows ±20% error on package calorie counts (the difference between labeled and measured calories, not counting fiber accounting quirks). Real variation averages about 8% for most products. Then there is rounding: a muffin labeled 300 calories may legally be 280 or 320.

Restaurant calorie counts are even worse. Calorie estimates for dishes can vary 50-100% based on actual portion size, preparation method, and ingredient variance. A “500-calorie chicken Caesar” served at one restaurant can easily be 750 calories at another.

The practical implication: do not chase exact calorie numbers. Track trends over weeks. If your body weight is moving in the direction you want, your numbers are “accurate enough.” If not, adjust in 100-200 kcal/day steps and observe.

Calculate your numbers

Our calorie calculator returns BMR, TDEE, and recommended calories for maintenance, mild weight loss, and faster weight loss. Plug in your age, weight, height, sex, and activity level, then use the number that matches your goal. Revisit every 4-6 weeks as your weight changes — the target shifts as the body changes. The math is simple; the consistency is the hard part.