Estimates for healthy adults, not medical advice.
TL;DR
Your TDEE is the number of calories you burn per day, training included. Eat at that number and your weight holds. Eat about 500 below it to cut, or about 250 above it to gain muscle with minimal fat. Recalculate every 10 to 15 pounds of weight change.
THE METHOD
HOW THE ORACLE counts.
The tool runs the Mifflin-St Jeor equation, published by Mifflin MD et al. in the American Journal of Clinical Nutrition, 1990 (PMID 2305711). The researchers measured resting metabolic rate in 498 healthy adults and built a formula that predicts it from four things you already know: weight, height, age, and sex. For men, that is 10 times weight in kilograms, plus 6.25 times height in centimeters, minus 5 times age, plus 5. For women, the final term is minus 161 instead.
That output is your BMR: the calories your body burns lying still, keeping the heart, lungs, brain, and body temperature running. Nobody lies still all day, so the calculator multiplies BMR by an activity factor, from 1.2 if you sit most of the day up to 1.9 if you train hard on top of a physical job. The product is your TDEE.
Enter a body fat percentage and the math switches to Katch-McArdle: 370 plus 21.6 times your lean mass in kilograms. Because it works from lean mass instead of total weight, it often fits lean, muscular people better; the standard equations were built on averages, and a lifter carrying a lot of muscle isn't average. The result card tells you which formula is active.
Every equation here is an estimate. Two people with identical stats can differ by a couple hundred calories a day in measured burn, and no calculator sees your genetics, your step count, or how honestly you picked your activity level. Treat the output as a well-placed starting point, then let two or three weeks of scale data correct it.
THE EQUATION
MEN
10 × kg + 6.25 × cm - 5 × age + 5
WOMEN
10 × kg + 6.25 × cm - 5 × age - 161
WITH BODY FAT %
370 + 21.6 × lean kg
THEN
× activity, 1.2 to 1.9
Mifflin-St Jeor, 1990 · 498 adults measured
THE ORACLE SPEAKS IN numbers.
THE READING
USING YOUR number.
Match the row to the goal. Maintenance means eating your TDEE: the scale stays roughly put, which is what you want when holding a physique or running a strength block. The cut row takes 500 calories off, a pace most people can hold while still training hard. The lean bulk row adds 250, enough surplus to support muscle growth without stacking on fat you'll have to diet off later.
Then check it against reality. Weigh yourself a few mornings a week under the same conditions and average each week. If the trend matches the plan, your number is right. If a cut stalls for two or three weeks, take off another 100 to 200 calories. If a bulk adds weight much faster than half a pound a week, trim the surplus. The calculator gets you to the right neighborhood; the scale finds the house.
One more honesty check: most people overrate their activity level. Training an hour a day does not make a desk worker very active for the other 23 hours. When two levels both look plausible, pick the lower one; overshooting maintenance quietly erases a cut. And do not stack trackers on top of this number. Your watch's calorie burn and this calculator measure overlapping things, so pick one source of truth and stay with it.
If you use a powder
PRIME Whey Protein
25g protein per serving, designed to help you hit your daily target inside whichever calorie number you picked above. Isolate first blend, 30 servings, full label on the tub.
View PRIME →Calories set the size of the change. Protein decides how much of that change is muscle, so run the protein calculator next and keep both numbers in the same plan. If you want formulas matched to a cut or a bulk, the goals page sorts our stacks by target, and the tools hub lists every calculator we have shipped.
AT THE ALTAR
QUESTIONS, answered.
What is TDEE?
TDEE stands for total daily energy expenditure: every calorie you burn in 24 hours, including your resting metabolism, digestion, daily movement, and training. It's the baseline number for any calorie plan, since eating above it adds weight over time and eating below it removes weight over time.
How accurate is a TDEE calculator?
Good enough to start, not gospel. Prediction equations like Mifflin-St Jeor land within roughly 10 percent of measured resting burn for most healthy adults in validation studies, and the activity multipliers add more guesswork. Run your number, eat to it for two or three weeks, watch the scale trend, then adjust.
How often should I recalculate my TDEE?
Whenever your body weight changes by about 10 to 15 pounds, or your training volume shifts for more than a few weeks. TDEE follows your mass and your activity, so a long cut lowers it and a productive bulk raises it. A 30-second recalculation keeps your targets honest.
Why is the cut set 500 calories below maintenance?
A 500-calorie daily deficit is the classic rule of thumb: it adds up to about 3,500 calories a week, roughly one pound of fat, while leaving enough food to train hard and keep protein high. Steeper cuts work but cost more muscle and adherence. Slower cuts also work; they just take longer.