What is the difference between BMR and TDEE?

BMR (basal metabolic rate) is the energy your body burns at complete rest just to stay alive — breathing, circulation, cell repair. TDEE (total daily energy expenditure) is your BMR multiplied by an activity factor, so it includes movement, exercise and digestion. TDEE is the number you actually eat to, not BMR.

Which formula does this calculator use?

It uses the Mifflin-St Jeor equation, the most accurate general-purpose BMR formula for healthy adults. If you supply a body fat percentage, it switches to the Katch-McArdle equation, which is based on lean body mass and tends to be more accurate for lean or muscular people.

How accurate is a calculated TDEE?

Equation-based estimates are typically within about 10 to 15 percent of measured values. They cannot account for genetics, thyroid function, medication or non-exercise activity (NEAT). Treat the number as a starting point: track your weight for two to three weeks and adjust calories up or down by 100 to 200 if the scale is not moving as expected.

How many calories should I eat to lose weight?

A moderate deficit of roughly 15 to 20 percent below your TDEE produces about 0.5 kg of fat loss per week without wrecking your energy or muscle. The calculator shows ready-made deficit targets and warns you if a target drops below the commonly recommended minimum of 1,500 kcal for men or 1,200 kcal for women.

What activity level should I choose?

Be honest and slightly conservative. Sedentary suits a desk job with little exercise; lightly active covers one to three workouts a week; moderately active is three to five sessions; very active is six to seven hard sessions; extra active is a physical job plus daily training. Most people overestimate, so when in doubt pick the lower option.

Is my data sent anywhere?

No. Every calculation runs entirely in your browser using JavaScript, and your inputs are saved only to this device via local storage so the form remembers them next visit. Nothing is uploaded, and you can clear it any time with the Reset button.

BMR & TDEE Calculator

This BMR & TDEE calculator turns four simple measurements — sex, age, height and weight — into the two numbers that drive every nutrition plan: your basal metabolic rate (the calories your body burns at rest) and your total daily energy expenditure (everything you burn in a full day). From there it builds a complete set of goal calorie targets for losing, maintaining or gaining weight, plus a macronutrient split and a 12-week weight projection. It works in metric or imperial, remembers your last entry, and runs 100% in your browser.

How it works

The calculator starts with the Mifflin-St Jeor equation, the formula most dietitians reach for because it predicts resting energy better than the older Harris-Benedict equation for modern adults:

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

If you enter a body fat percentage, the tool instead uses the Katch-McArdle equation, which is built on lean body mass (BMR = 370 + 21.6 × lean mass in kg) and is more accurate for very lean or muscular bodies. Your BMR is then multiplied by an activity factor — from 1.2 for sedentary up to 1.9 for extra active — to give your TDEE, the calories that keep your weight stable.

Each goal target adjusts your TDEE by a fixed percentage. A 500 kcal daily deficit is roughly 0.5 kg of fat per week, since one kilogram of body fat stores about 7,700 kcal. The macro panel splits your maintenance calories into grams of protein, carbohydrate and fat at 4, 4 and 9 kcal per gram. Imperial inputs are converted internally: height in feet and inches becomes centimetres, and pounds become kilograms, so the equations always run on canonical metric values.

Example

A 30-year-old man who is 178 cm tall, weighs 80 kg and is moderately active:

BMR (Mifflin-St Jeor): about 1,780 kcal/day
TDEE at ×1.55: about 2,760 kcal/day
To lose ~0.5 kg/week: about 2,275 kcal/day
To gain lean mass: about 3,035 kcal/day

Switch the same person to sedentary and TDEE drops to roughly 2,135 kcal — which is exactly why your activity-level choice matters more than any other input. Tweak the numbers, pick a goal row, and download the full breakdown as CSV.

Every figure is calculated locally and nothing is uploaded.