Every body burns energy all day long, and knowing roughly how much you burn in a day — your Total Daily Energy Expenditure, or TDEE — is the single most useful number for weight management. Everything a diet plan, fitness coach, or nutrition app eventually returns to is a comparison against this figure. Eat at it and your weight holds steady. Eat below it and you lose. Eat above it and you gain. This calculator estimates your TDEE from a handful of personal measurements using the carefully chosen Mifflin-St Jeor equation, then translates that number into practical daily targets for maintenance, cutting, and muscle building.
What the letters actually mean
Your body spends energy on three broad kinds of work. Basal metabolic rate, or BMR, is the baseline: the energy needed to power your heart, lungs, brain, liver, and every cell at complete rest. This is normally the largest chunk, often sixty to seventy percent of your day. Above that sits the thermic effect of food, the energy spent digesting what you eat, and finally physical activity, from a morning walk to a full strength workout. Total Daily Energy Expenditure is simply the sum of all three, and it is the number that answers the real question: how many calories can I eat and hold my current weight?
That is why a TDEE estimate beats a raw BMR number for everyday decisions. Knowing you burn seventeen hundred calories at rest tells you little about your lunch budget; knowing your total daily burn is twenty-five hundred makes the answer concrete. Weight change is arithmetic over weeks — roughly 3,500 calories make a pound, more precisely about 7,700 calories per kilogram — and TDEE is the reference side of that equation you control the input to.
The Mifflin-St Jeor equation
This calculator bases its resting estimate on the Mifflin-St Jeor equation from 1990, which today is the most widely used and best-regarded formula for healthy adults. In metric units it reads:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Notice the ingredients: weight and height raise the estimate, age lowers it slightly each decade, and the sex constant — plus five for men, minus one hundred and sixty-one for women — captures typical differences in lean body mass. The equation was designed for modern, less active populations, and studies consistently show it matches measured resting values closer than older formulas such as Harris-Benedict. For a thirty-year-old man standing 170 cm tall and weighing 70 kg, the resting burn works out to roughly 700 + 1062.5 − 150 + 5 ≈ 1,618 calories per day.
Adding in your activity level
Resting burn is only the starting point, so the calculator multiplies the BMR by an activity factor that estimates everything else: walking between meetings, cooking, commuting, workouts, and the calories digestion itself consumes. The standard multiplier table appears as a list in the tool:
- Sedentary 1.2 — desk work, little or no exercise
- Lightly active 1.375 — light exercise one to three days a week
- Moderately active 1.55 — moderate exercise three to five days a week
- Active 1.725 — hard exercise six to seven days a week
- Very active 1.9 — hard daily exercise plus a physically demanding job
- Extra active 2.0 — very intense daily training or a strenuous physical career
The single biggest source of error in any TDEE tool is picking the wrong band. Most people overestimate how active they really are. If you work at a desk and train three times a week, you are typically "lightly to moderately active," not "active." Honest self-assessment matters more than tweaking the equation, because choosing 1.55 instead of 1.75 on a 1,600-calorie BMR changes your daily target by more than three hundred calories.
Three targets that make the number useful
Rather than leaving you with a raw number, the calculator layers three practical goals over the same estimate. The headline figure is your maintenance budget, the calories that hold your current weight steady. Cutting an aggressive five hundred keeps that figure if weight loss is the goal, since a five hundred calorie daily deficit converts to about half a kilogram, or just over a pound, of fat per week — a pace that preserves muscle and stays sustainable. Bulking adds a lean three hundred calories instead, positioning your body to build muscle when paired with strength training, while keeping fat gain modest.
These aren't guesses layered on guesses; they are linear offsets of the same TDEE. The deficit and surplus both simply shift the maintenance line, which is why the tool shows all three figures side by side. Choose the target that matches your goal, then re-check it as your weight drifts, because a smaller person burns less than a larger one and the targets move with you.
Reading the donut and gauge
Two visual aids place the numbers in context. The donut splits your daily burn into resting metabolism and everything on top of it, making it obvious that the majority of your calories go to baseline function regardless of activity. The gauge then locates your TDEE along a band that runs from low through moderate, high, and very high, so you can quickly see whether your input combination describes a lightly burning desk worker or a very active athlete.
A quick worked example
Take a 28-year-old woman, 165 cm tall, 60 kg, moderately active at a multiplier of 1.55. Her resting burn is 600 + 6.25 × 165 − 140 − 161 ≈ 730. For clarity, the full computation is 600 plus 1031.25 minus 140 minus 161, which lands near 1,330 calories. Scaling by 1.55 gives a maintenance target around 2,062 calories daily. A five hundred deficit suggests roughly 1,562 to lose about half a kilogram per week, and a lean surplus of three hundred suggests about 2,362 to build muscle. Every one of these numbers inherits the same estimate, so they always move together.
Accuracy expectations and what can shift the number
Mifflin-St Jeor is good but not perfect. For roughly two-thirds of healthy adults it lands within about ten percent of laboratory-measured resting burn, and real daily burn varies further with muscle mass, hormones, sleep, thyroid function, and how much you move on a given day. Because the outcome feeds directly into eating plans, the practical approach is to treat the estimate as a hypothesis and verify it with reality. Track your weight weekly for two to three weeks while eating a fixed number of calories near your target. If the scale is stable, the estimate is right; if you lose when you intend to maintain, add a hundred calories and revisit in another fortnight.
Body composition deserves a special mention here, because it is the biggest hidden variable behind any formula. Muscle is metabolically expensive tissue: it demands more calories at rest than the same mass of fat does, which is why two people of identical height, weight, and age can honestly burn different daily totals. Formulas such as Mifflin-St Jeor cannot see that difference, so a heavily muscled athlete may find the estimate low, while someone with a higher fat percentage may find it high. That is exactly why tracking beats trusting: your personal trend line settles the argument that a population formula cannot.
One more caution deserves explicit mention. If your activity burn is small, subtracting the full five hundred can push the cutting figure below your BMR, which is unsustainable for most people. In that situation, prefer a smaller two-to-three-hundred deficit and add a little daily movement, rather than starve the baseline your body needs for recovery and health. The scale should move steadily but not drastically: losing a kilogram a week is generally too fast unless you are carrying considerable weight to begin with.
Making the estimate stick
For the best results, update the calculator whenever your body changes. Losing ten kilograms lowers your resting estimate by roughly one hundred sixty calories, and gaining muscle has the opposite effect because muscle tissue raises your burn even at rest. Re-entering your current weight each month keeps the three targets honest, and pairing the maintenance figure with a macro split lets you plan complete meals rather than raw calories alone. Consistency in how you log and when you weigh — same time, same scale, wearing similar clothing — removes most of the noise that makes week-to-week comparisons confusing.
It is also worth remembering where the estimate does and does not apply. Children, pregnant women, and anyone recovering from illness have energy needs that standard equations model poorly, and extremely muscular or very elderly individuals sit on the edge of the formula's comfort zone. For those groups the number is still useful as a rough beginning, but a dietitian or doctor can measure needs far more precisely. For the broad middle of healthy adults, this calculator captures the essentials: your baseline, your activity, and the targets you can actually act on.
TDEE is a compass, not a verdict. It tells you which direction to point your eating and how far the dial must move to reach your goal, and it does so from nothing more than measurements you already know. Enter your details, read your three targets, and let the arithmetic do the steering while the weekly scale confirms the route.
Disclaimer
Results are provided as estimates for informational purposes only and may be inaccurate. Always verify outcomes with a qualified professional before making financial or personal decisions based on these calculations.