How many calories should you actually eat? Enter your stats and activity level, and get your BMR (what you burn at rest), your maintenance calories (TDEE), and the daily targets for losing or gaining weight at a sensible pace — in US or metric units, live as you type.
How it works
The engine uses the Mifflin-St Jeor equation, the standard BMR formula most clinical nutrition guidelines adopted after it outperformed older formulas in validation studies. BMR is what your body burns keeping the lights on: heart, brain, breathing, temperature. Multiply it by your activity level and you get TDEE — total daily energy expenditure, the number where your weight stays flat. The weight targets adjust TDEE by ±250 and ±500 calories, which works out to about half a pound and a pound a week, since a pound of body fat stores roughly 3,500 calories.
Reading the numbers
A 35-year-old man at 180 lb and 5’10” with a moderately active life has a maintenance target near 2,725 calories; a pound-a-week loss plan sits around 2,225. Women typically land 300-500 lower on the same stats — mostly the formula’s height and body-composition terms. Sedentary vs very active swings TDEE by about 700 calories a day, which is why exercise and NEAT (the calories you burn just moving around) matter more than most people think. If “extreme loss” dips you under about 1,200 (women) or 1,500 (men) calories, pick a gentler target — very low intakes lean out muscle and adherence both.
Averages hide individual variation: genetics, muscle mass, and honest activity reporting can each move your true TDEE a few hundred calories either way — treat two weeks of scale data as the ground truth, and this estimate as the starting hypothesis. Built in-house in plain JavaScript — no widgets, no tracking, nothing you type leaves your device. This tool is for information only and is not medical or dietary advice.