You want to know how much to eat. Not an estimate. The actual number. Enter your stats and this calculator returns your TDEE — total daily energy expenditure — plus calorie targets for weight loss, maintenance, and muscle gain based on the Mifflin-St Jeor equation, the most accurate BMR formula for non-athlete adults according to the American Council on Exercise.
Estimated Daily Macros (Maintenance)
BMR calculated using the Mifflin-St Jeor equation, published by MD Mifflin et al. in the American Journal of Clinical Nutrition, 1990. Activity multipliers sourced from American Council on Exercise (ACE) standard guidelines. Macro targets based on ISSN position stand on protein requirements (1.6-2.2g/kg for active individuals). Last verified May 2026.
You want to lose weight. You find a TDEE calculator, plug in your numbers, get a result of 2,350 calories, eat 1,950, and after three weeks of perfect tracking — nothing happens. This is the most common TDEE experience, and it has nothing to do with the formula being wrong.
TDEE stands for Total Daily Energy Expenditure. It is the number of calories your body burns in 24 hours including everything — breathing, digestion, moving around, and any intentional exercise. Eat below it and you lose weight. Eat above it and you gain. Eat at it and you maintain. Simple in theory. The problem is that the activity multiplier — the part that converts your resting metabolic rate into your full daily burn — is where almost everyone makes an error.
The Mifflin-St Jeor equation is more accurate than the older Harris-Benedict formula by approximately 5% according to a 2003 systematic review in the Journal of the American Dietetic Association. This doesn't sound like much, but 5% on a 2,000-calorie TDEE is 100 calories per day — enough to explain a plateau.
| Activity Level | Multiplier | Who It Fits | Who Picks It Incorrectly |
|---|---|---|---|
| Sedentary | 1.2 | Desk job, no intentional exercise | Almost nobody picks this |
| Lightly Active | 1.375 | Exercise 1-3 days/week, desk job | Most gym-goers 3x/week should be here |
| Moderately Active | 1.55 | Moderate exercise 3-5 days/week | Most people select this — often too high |
| Very Active | 1.725 | Hard exercise 6-7 days/week | People with desk jobs who train 5x/week |
| Extra Active | 1.9 | Physical labour + daily training | Rare — construction workers who also train |
Someone with a desk job who goes to the gym 4 times per week is probably a 1.375 to 1.45, not a 1.55. Most calculators don't explain this clearly. If your results seem too high and you're not losing weight on a 400-calorie deficit, try 1.375 and track for two weeks.
You start a diet, you're eating 400 below TDEE, you lose weight for 5 weeks. Then nothing. You didn't eat more. You didn't slack on training. The scale just stopped. This is adaptive thermogenesis — and it's the part of TDEE that every calculator misses because no equation can predict it for your specific body.
When you sustain a calorie deficit, your body doesn't just burn fat and move on. It reduces its energy expenditure as a survival mechanism. Research published in Obesity Reviews (Johannsen et al.) shows moderate calorie restriction triggers an additional metabolic slowdown of 100–300 calories per day above what weight loss alone would predict. This is called metabolic adaptation, and it's separate from the reduction in TDEE that happens simply because you weigh less.
The Minnesota Starvation Study — the most comprehensive study of calorie restriction ever conducted — showed a 40% reduction in resting metabolic rate after 24 weeks of severe restriction. Most of that was explained by weight loss, but a meaningful portion was adaptive. In normal dieting scenarios, the adaptive component is smaller but still enough to stall progress.
NEAT (Non-Exercise Activity Thermogenesis) is all the movement that isn't structured exercise — fidgeting, walking around your home, small gestures, standing instead of sitting. NEAT can account for 200–500 calories per day and varies enormously between individuals at the same body weight.
Here's what most people don't know: in a calorie deficit, your body automatically reduces NEAT without you noticing. You fidget slightly less. You sit a little more often. You walk a little slower. A 2012 study in the American Journal of Clinical Nutrition found that NEAT can decrease by 100–250 calories per day during active weight loss. You didn't choose this. It happens automatically as a calorie conservation response.
Your initial TDEE calculation is accurate for your starting weight and activity level. As you lose weight, it becomes progressively less accurate. A person who loses 25 pounds has a meaningfully lower TDEE than when they started — often 150–250 fewer daily calories. Continuing to eat at your original deficit target will gradually shrink your actual deficit, eventually to zero.
| Trigger | Why Recalculate | Expected TDEE Change |
|---|---|---|
| Every 10–15 lbs lost | Lower body weight = lower BMR | -75 to -150 cal/day |
| Progress stalls 2+ weeks | May indicate adaptive thermogenesis | Reduce target by 100–150 cal |
| Activity level changes | New job, injury, new training block | ±200 to ±400 cal/day |
| Age milestone (every 5 yrs) | BMR decreases ~2% per decade after 30 | -50 to -100 cal/day |
A 400-calorie daily deficit produces about 0.8 pounds of fat loss per week — slower than the dramatic results people want, fast enough to actually work without muscle loss. Deficits beyond 500 calories per day start to produce meaningful muscle loss even with adequate protein, because the body increasingly uses muscle protein for fuel when calories are very low.
The maths: 3,500 calories = approximately 1 pound of fat. A 400-calorie daily deficit = 2,800 weekly deficit = 0.8 lbs/week. Over 12 weeks: roughly 9.6 lbs. Slower than a 1,000-calorie deficit, but you'll keep the weight off because you've preserved metabolic rate and muscle mass.
The natural rate of muscle gain for a drug-free, experienced trainee is approximately 0.5–1 pound per month. To build 1 pound of muscle requires roughly 2,000–2,500 extra calories above maintenance over the month — which works out to a daily surplus of just 70–85 calories. Even being generous, a 250-calorie daily surplus is more than enough to maximise muscle growth.
Everything above that 250–350 calorie surplus goes primarily to fat storage. The "dirty bulk" approach of eating 800 calories above TDEE doesn't build muscle faster — it just adds fat that then needs to be cut later. If muscle gain with minimal fat is the goal, 200–350 calories above TDEE is the evidence-based target.
| Profile | Estimated BMR | Sedentary TDEE | Moderately Active TDEE |
|---|---|---|---|
| Female, 25, 5'4", 130 lbs | 1,390 | 1,668 | 2,155 |
| Female, 35, 5'6", 155 lbs | 1,497 | 1,796 | 2,320 |
| Female, 45, 5'5", 145 lbs | 1,409 | 1,691 | 2,184 |
| Male, 25, 5'10", 170 lbs | 1,847 | 2,216 | 2,863 |
| Male, 35, 5'11", 190 lbs | 1,966 | 2,359 | 3,047 |
| Male, 45, 5'10", 185 lbs | 1,857 | 2,228 | 2,878 |
These are starting estimates. Your actual maintenance calories will differ from any table because individual metabolic variance runs ±10% on the Mifflin-St Jeor formula. Two weeks of consistent calorie tracking at a fixed number with daily weigh-ins gives you a reliable personal calibration no formula can match.
For women, TDEE is not a fixed daily number. Research from Strong Curves and clinical nutrition literature shows total daily energy expenditure fluctuates by roughly 5–10% across the menstrual cycle, driven by hormonal changes. During the luteal phase (roughly days 15–28), resting metabolic rate is slightly elevated — some women burn 100–200 extra calories per day compared to the follicular phase. This is why tracking weight daily shows apparent fluctuations that have nothing to do with fat gain or loss. Weekly weight averages are far more reliable than daily weigh-ins for women tracking progress against their TDEE.
Practically, this means your TDEE target from one week may not perfectly match your energy needs the following week. If you consistently feel very hungry in the second half of your cycle, eating at maintenance (or 100–150 calories above your fat-loss target) during those days often improves adherence without derailing progress.
This is the TDEE insight most people find genuinely surprising. For a typical gym-goer training four times per week, structured exercise (EAT) contributes roughly 5–10% of total TDEE. NEAT — the calories burned through daily movement that is not exercise — contributes 15–30%. Four one-hour gym sessions burn approximately 800–1,200 calories per week. But an active person who walks throughout the day, takes stairs, and moves regularly can burn 500–800 more calories per week than a sedentary person of the same body weight — without a single gym session.
This explains why two people with identical workout schedules can have dramatically different results. The one who walks to work, paces during phone calls, and stands at their desk is accumulating hundreds of extra calories of NEAT burn daily. Increasing daily steps to 8,000–10,000 per day is often more impactful for fat loss than adding an extra training session.
Metabolic rate declines roughly 2% per decade after age 30, driven primarily by muscle loss rather than aging itself. A 50-year-old at the same weight and activity level as a 30-year-old will have a TDEE approximately 200–300 calories lower. This is not inevitable — it is largely a consequence of losing lean muscle mass, which is far more metabolically active than fat tissue. Each pound of muscle burns roughly 6–10 calories per day at rest. Each pound of fat burns 2–3. Resistance training that maintains or builds muscle mass is the single most effective counter to age-related TDEE decline. Women going through perimenopause and menopause face an additional layer: hormonal changes can reduce metabolic rate further and shift where the body stores fat. This is why TDEE recalculation every year after 40 is more important than it is at 25.