TDEE Calculator Online

How to Calculate TDEE Online

1. Enter Sex, Age, Weight, and Height: Pick male or female (the constant differs by 166 kcal in the Mifflin-St Jeor equation), then enter age in years, weight in kg or lb, and height in cm or ft/in. Toggle units anytime; the calculator converts internally.
2. Pick an Activity Level: Choose Sedentary (1.2 — desk job, no workouts), Lightly Active (1.375 — light exercise 1-3 days/week), Moderately Active (1.55 — moderate exercise 3-5 days/week), Very Active (1.725 — hard exercise 6-7 days/week), or Extra Active (1.9 — physical job plus daily training). These are the Harris-Benedict multipliers in standard use since 1984.
3. Optional — Add Body Fat % for Katch-McArdle: If you know your body fat percentage from a DEXA, BodPod, or caliper measurement, enter it to switch from Mifflin-St Jeor to Katch-McArdle (BMR = 370 + 21.6 × lean body mass in kg). Skip if you don't have a measurement — caliper-from-mirror guesses do more harm than good.
4. Read Your BMR and TDEE: The calculator displays BMR (calories at complete rest), TDEE (BMR × activity multiplier), and target ranges for cutting (−500 kcal), maintenance, and bulking (+300 to +500 kcal). Nothing is uploaded — all math runs in your browser.

Why Calculate TDEE?

Total Daily Energy Expenditure is the calories you burn in 24 hours including basal metabolism, the thermic effect of food (~10%), exercise, and non-exercise activity (NEAT — fidgeting, walking, posture). It's the starting point for any deliberate body-composition change: eat below TDEE to lose fat, eat above to gain muscle, eat at it to recomp or maintain. A calculator estimate sits within roughly ±10% of measured expenditure if you're honest about activity — and most people overestimate.

• Fat loss planning — A 500 kcal/day deficit yields 0.45 kg (1 lb) of fat loss per week (3,500 kcal ≈ 1 lb of body fat, the classic Wishnofsky figure; the real number is significantly less because of metabolic adaptation — the 3,500 kcal rule overestimates actual fat loss by 30–50% over sustained deficits). Knowing your TDEE turns "eat less" into a specific calorie target.
• Muscle-gain (lean bulk) — Hypertrophy needs a small surplus, typically 200-500 kcal over TDEE. Bigger surpluses add fat without faster muscle gain past the beginner phase.
• Recomp / maintenance — Eating at TDEE while training and hitting 1.6-2.2 g protein per kg bodyweight lets trained lifters slowly trade fat for muscle.
• Marathon, ultra, or hard training blocks — Endurance athletes routinely burn 3,500-6,000 kcal on long days; a baseline TDEE plus session calories prevents under-fueling and RED-S (relative energy deficiency in sport).
• Medical / clinical — Dietitians and registered nurses use Mifflin-St Jeor for inpatient calorie prescriptions; the Academy of Nutrition and Dietetics (AND, formerly American Dietetic Association until 2012) recommended it over Harris-Benedict in 2005 for non-obese adults.
• Fitness-tracker reality check — Apple Watch and Fitbit "active calories" estimates drift 20-90% from indirect calorimetry depending on activity; a TDEE baseline keeps you from chasing fictional numbers.

Activity Multiplier Reference

BMR Equation Comparison

W = weight kg, H = height cm, A = age years. Mifflin-St Jeor was the Academy of Nutrition and Dietetics' evidence-based recommendation (AND; formerly the American Dietetic Association, renamed 2012) for non-obese adults and outperformed Harris-Benedict in head-to-head studies — within ±10% of measured RMR in roughly 50.4% of overweight and obese patients vs 36.8% for Harris-Benedict.

Frequently Asked Questions

Mifflin-St Jeor or Harris-Benedict — which equation should I use?

Mifflin-St Jeor (1990) is more accurate for almost everyone. In a 2005 Academy of Nutrition and Dietetics (AND) systematic review and follow-up studies, Mifflin-St Jeor predicted resting metabolic rate within ±10% of indirect calorimetry in about 50-71% of subjects, beating the 1919 and 1984 Harris-Benedict equations. The newer equation was developed on a more representative population (498 subjects, both obese and non-obese). Use Harris-Benedict only if you're replicating older clinical literature.

Why is my calculated TDEE different from what my Apple Watch or Fitbit says?

Wrist-worn trackers estimate calories from heart rate and accelerometer data, then add a BMR estimate. Independent validation studies have found error rates of ±20-90% depending on the activity — cycling, weightlifting, and strength training are especially poor. The Apple Watch tends to over-report walking calories and under-report heavy lifting. Use the calculator's TDEE as your planning baseline; let weight-change feedback over 3-4 weeks tell you which number was closer to truth.

What cutting and bulking deficit/surplus should I use over my TDEE?

For fat loss, a 300-500 kcal/day deficit (roughly 10-20% of TDEE) is sustainable and limits lean-mass loss; aggressive cuts of 750+ kcal accelerate fat loss but raise the risk of muscle loss, sleep disruption, and rebound. For lean bulking, 200-500 kcal/day above TDEE (5-15% surplus) is enough for hypertrophy in most natural lifters; bigger surpluses past the early novice phase mostly add fat. Keep protein at 1.6-2.2 g/kg bodyweight either way.

How is lean body mass calculated for Katch-McArdle?

Lean body mass = total weight × (1 − body fat fraction). For an 80 kg person at 15% body fat: LBM = 80 × 0.85 = 68 kg, and BMR = 370 + 21.6 × 68 = 1,839 kcal. The catch is that body fat percentage itself is hard to measure: DEXA is the practical gold standard (±2% error), BodPod and hydrostatic weighing are similarly accurate, smart scales using bioimpedance commonly drift 4-8% from DEXA, and 3-site or 7-site caliper readings depend heavily on the technician. Skip Katch-McArdle if your body fat number is a guess — Mifflin-St Jeor will be closer.

Why do activity multipliers stop at 1.9? Are bodybuilders or endurance athletes higher?

The 1.2-1.9 range was set to cover sedentary adults through competitive athletes in standard published tables. Multipliers above 1.9 do exist in sports nutrition — Tour de France riders routinely hit 4,500-9,000 kcal/day (TDEE ratios of 2.5-4× BMR), and military Ranger School candidates can reach similar numbers. For these populations, calculate baseline TDEE with the 1.9 multiplier, then add specific session-by-session expenditure from power meters, HR-based VO₂max estimates, or activity-specific tables. A general-purpose calculator can't catch these correctly.

Why am I gaining or losing weight differently than my TDEE math predicts?

Three usual culprits. First, calorie tracking is noisy: USDA labels are allowed up to ±20% error, restaurant portions are typically under-reported by 20-50%, and most people undercount by 200-500 kcal/day without a food scale. Second, metabolic adaptation: in a sustained deficit, NEAT and thyroid output drop and BMR can fall 5-15% beyond what the formulas predict. Third, the activity multiplier you picked may not match reality — most people round up. Reweigh weekly, track trends over 3-4 weeks before adjusting, and use the trend slope (not single-day swings) as feedback.

Should pregnant or breastfeeding women use a TDEE calculator?

Not on its own. Pregnancy adds roughly 340 kcal/day in the second trimester and 450 kcal/day in the third (Institute of Medicine 2002 estimates); lactation adds another 330-400 kcal/day for the first 6 months. These numbers vary widely by activity, multiple pregnancies, and milk volume. Use the calculator only to estimate non-pregnant baseline and add the relevant adjustment with guidance from an OB/GYN or registered dietitian — not a fitness app.

Does TDEE change with age, and how fast?

Yes, but slower than most assume. A 2021 Science paper from Pontzer et al. analyzed 6,400 subjects and found energy expenditure is stable between roughly age 20 and 60 (after correcting for body composition), then declines about 0.7% per year past 60. Most age-related weight gain comes from reduced activity and muscle loss, not BMR collapse. Recheck your TDEE every 5-10 years or after a 5+ kg body-composition change.

How does this calculator compare to medical-grade metabolic testing?

Indirect calorimetry — measuring oxygen consumed and CO₂ exhaled under a hood at rest — is the clinical gold standard for BMR (~±5% error). Test centers and some hospitals offer it for $80-200. DEXA scans give body composition for Katch-McArdle. A formula-based estimate from this calculator is free, instant, and usually within ±10% of measured values if you pick the right activity level — good enough for diet planning. Pay for indirect calorimetry only if you have a stalled cut, suspected metabolic disorder, or you're a competitive athlete fine-tuning a peak.