BMR versus TDEE
Your Basal Metabolic Rate is the energy your body uses at complete rest just to keep organs running. Total Daily Energy Expenditure adds everything on top of that: walking, working, exercising, and even digesting food. Because most people are not bedridden, TDEE is the more useful number for planning meals. We reach it by multiplying BMR by an activity factor between 1.2 for sedentary and 1.9 for very active.
Choosing an activity level
Be honest about how much you actually move. A desk job with two or three light workouts a week is closer to lightly active than moderate. Overstating activity is the most common reason calorie targets stall, because it inflates your maintenance number and quietly erases the deficit you were aiming for. When in doubt, pick the lower level and adjust after a couple of weeks of real-world results.
Turning calories into results
To lose about a pound a week, aim for roughly 500 calories below your TDEE each day; to gain, add a similar surplus. Pair the target with enough protein — around 0.7 to 1 gram per pound of body weight — to protect muscle. Weigh yourself a few mornings a week and average the readings, since day-to-day fluctuations from water and food can easily hide steady progress. Pair the target with your BMI to see where your weight sits relative to the healthy range.
More worked examples
A 42-year-old woman who is 5 ft 5 in, weighs 150 lb, and exercises one to three days a week (Light) has a BMR of 1,341 cal and maintenance calories (TDEE) of 1,844 cal/day. The 500-calorie targets are 1,344 cal/day to lose about a pound a week and 2,344 cal/day to gain, and the protein target is 109 g/day.
Why the activity level matters: a 28-year-old man who is 6 ft 0 in and weighs 185 lb has a BMR of 1,847 cal. Marked Sedentary, his TDEE is 2,217 cal/day; marked Active, it is 3,186 cal/day. The same body gets very different targets depending on the activity level you choose, which is why picking it honestly matters.
When to use this calculator
Use it to set a starting calorie target for maintaining, losing, or gaining weight, to see how much a change in activity shifts your needs, or to estimate a daily protein target from your body weight. Treat the numbers as a starting point and adjust after a few weeks of tracking your actual weight.
Common mistakes
Choosing an activity level that counts your workouts and then adding exercise calories on top double-counts the same activity. Using an old weight is another frequent error: as your weight changes, your BMR and TDEE change too, so rerun the calculator after a noticeable change. Mixing units also causes trouble; check the Units setting before you enter height and weight. Finally, a target that falls below the common minimums is flagged in the result panel rather than recommended, so treat that warning as a reason to slow down.
Reading the result panel
The headline is your maintenance calories, the TDEE. Below it, the panel lists your BMR at rest, the targets for losing or gaining about a pound a week, and a protein target calculated at 1.6 grams per kilogram of body weight. All values are rounded to whole numbers for display.