TDEE Calculator

What is TDEE?

TDEE (Total Daily Energy Expenditure) is the total calories your body burns in a day. It's made up of: BMR (Basal Metabolic Rate): calories burned at complete rest just keeping you alive (breathing, circulation, organ function). Typically 60-70% of TDEE. TEF (Thermic Effect of Food): calories burned digesting food. About 10% of TDEE. Protein has highest TEF. NEAT (Non-Exercise Activity Thermogenesis): fidgeting, walking, daily movement. Highly variable — NEAT can range from 15% to 50% of TDEE between individuals, which is part of why two people of similar size and activity level can have noticeably different total energy needs.

What do I need to know about Calculating BMR?

The Mifflin-St Jeor equation is the most accurate for most people: men: BMR = (10 × weight kg) + (6.25 × height cm) - (5 × age) + 5. women: BMR = (10 × weight kg) + (6.25 × height cm) - (5 × age) - 161. Example (35yo man, 75kg, 178cm): BMR = 750 + 1112.5 - 175 + 5 = 1,692 kcal/day. This is what he'd burn lying in bed all day. Other equations: Harris-Benedict (older, slightly less accurate). Katch-McArdle (uses body fat % — more accurate if you know your body fat). For most people without a body fat percentage measurement, the Mifflin-St Jeor equation remains the most accurate and widely recommended standard formula to use instead.

What should I know about Activity Multipliers?

TDEE = BMR × activity multiplier. The multipliers: sedentary (×1.2): desk job, minimal movement, no exercise. Lightly active (×1.375): light exercise 1-3 days/week, or active job with little formal exercise. Moderately active (×1.55): moderate exercise 3-5 days/week. Very active (×1.725): hard exercise 6-7 days/week. Extremely active (×1.9): physical job plus daily training, or twice-daily training. Choosing accurately: most people OVERESTIMATE their activity level. If unsure, pick the lower option — overestimating activity level is one of the most common reasons people fail to lose weight despite believing they're in a calorie deficit.

What should I know about Setting Calorie Targets?

Once you know TDEE, set your target based on goals: weight loss: eat below TDEE. A deficit of 500 kcal/day ≈ 0.5kg/week loss (1 kg fat ≈ 7,700 kcal). 250 kcal deficit ≈ 0.25kg/week (gentler, more sustainable). Don't go too aggressive — very large deficits cause muscle loss, metabolic slowdown, and rebound. Weight gain (muscle): eat above TDEE. A surplus of 250-500 kcal/day supports lean gains. Larger surpluses add more fat than muscle. Combine with resistance training and adequate protein. Maintaining consistency with the plan matters more than getting the exact calorie number perfectly right from the outset — adjust based on real-world results over a few weeks.

What should I know about NEAT — The Overlooked Calorie Burner?

Non-Exercise Activity Thermogenesis (NEAT) covers all the energy spent on movement that isn't formal exercise — fidgeting, standing versus sitting, taking the stairs, walking around the house, even the subtle restlessness of an energetic personality. Research on NEAT has found it can vary by several hundred calories a day between individuals of similar size and formal activity levels, and it's one of the biggest hidden reasons two people with the same TDEE calculator inputs can have genuinely different real-world calorie needs. NEAT also responds to diet: when calorie intake drops substantially, NEAT tends to fall too — people unconsciously move less, fidget less and take smaller steps, partially offsetting the calorie deficit without being noticed, which is one contributor to weight loss plateaus beyond simple metabolic adaptation. This is why advice to 'move more' during a diet isn't only about deliberate exercise sessions; consciously maintaining daily incidental movement (standing meetings, walking calls, taking stairs) can meaningfully support a calorie deficit by counteracting the body's unconscious tendency to conserve energy through reduced NEAT when food intake falls.

What should I know about Metabolic Adaptation During Dieting?

When calorie intake drops below what the body is used to, total daily energy expenditure doesn't stay fixed — it falls to some degree in response, a process known as metabolic adaptation (sometimes called "starvation mode," though that term overstates it). Part of this is simply mechanical: a smaller body burns fewer calories at rest and during movement, so TDEE naturally decreases as weight is lost. But research also shows an additional adaptive component beyond what reduced body size alone explains, including lower NEAT, small drops in resting metabolic rate beyond predicted values, and reduced levels of hormones like leptin and thyroid hormone that regulate energy use. This is a normal, usually modest, physiological response rather than a sign that dieting has "broken" metabolism, and most of it reverses once calorie intake returns to maintenance levels. In practice, it means calorie targets calculated at the start of a diet often need recalculating every few weeks as weight drops, since the TDEE figure that applied at the heavier starting weight will overestimate needs later in a sustained deficit.

Worked Example: Calculating Full TDEE Step by Step

Take a 30-year-old woman, 65kg, 165cm, moderately active (exercising 3-5 days/week). Using Mifflin-St Jeor: BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1,031.25 − 150 − 161 = 1,370 kcal/day. Applying the moderately active multiplier (×1.55): TDEE = 1,370 × 1.55 = 2,124 kcal/day.

This 2,124 kcal figure is her estimated maintenance intake — eating consistently around this level over several weeks should keep weight roughly stable, with the usual day-to-day fluctuation from water and digestion.

Doubly Labelled Water and Other Ways TDEE Is Actually Measured

Every formula-based TDEE estimate, including the one this calculator produces, is ultimately a population-average approximation — the only way to measure an individual's true total energy expenditure directly is doubly labelled water, a research technique in which a person drinks water containing safe, trace amounts of stable (non-radioactive) hydrogen and oxygen isotopes, and the rate those isotopes are eliminated in urine over one to two weeks reveals actual carbon dioxide production and therefore total energy expenditure. It's considered the gold standard in nutrition science precisely because it captures real-world NEAT, exercise and metabolic variation that no formula can see, but the cost (typically several hundred pounds per test) and need for mass spectrometry lab analysis make it impractical outside research settings. For everyday use, the practical substitute is what this calculator's own guidance recommends: use the formula estimate as a starting point, then calibrate against two to three weeks of real-world weight and intake tracking.

Why TDEE Calculators From Different Formulas Can Disagree by 100-300 Calories

Entering the same height, weight, age and activity level into different TDEE calculators can produce results that differ by 100-300 kcal/day, which understandably makes people doubt the numbers — but this is an expected consequence of which underlying formula is used, not a sign that any particular calculator is wrong. Mifflin-St Jeor (used here) is generally considered the most accurate equation for the general population without a known body fat percentage, and has outperformed the older Harris-Benedict equation in multiple validation studies, which tends to overestimate BMR by roughly 5-15% in modern populations partly because it was developed from a population a century ago. Katch-McArdle, which factors in lean body mass rather than total weight, can be more accurate again for people who know their body fat percentage, particularly athletic individuals with more muscle than the formula's weight-only alternatives assume. None of these differences matter much in practice if you treat the result as a starting estimate to be refined against your own tracked data, rather than a precise, final number.

TDEE and Weight Loss Plateaus

A calorie deficit calculated from an initial TDEE estimate often stops producing weight loss after several weeks or months, even without any change in diet or exercise, and this is largely because TDEE itself falls as body weight falls. A smaller body simply burns fewer calories at rest and during activity than a larger one, so the same calorie intake that created a deficit at the starting weight gradually becomes closer to maintenance as weight is lost. On top of this mechanical effect, metabolic adaptation can push resting metabolic rate down by a further 5-15% beyond what reduced body size alone would predict, as the body responds to a sustained deficit by becoming modestly more energy-efficient. Together, these two effects mean a calorie target that worked well in month one typically needs to be recalculated and reduced somewhat by month three or four to maintain the same rate of loss — a genuine plateau in progress despite consistent effort, rather than a sign that the approach has stopped working altogether.