BMR & TDEE: How Many Calories Do You Need a Day?

BMR vs TDEE: What's the Difference?

BMR (Basal Metabolic Rate) is the number of calories your body would burn in a full day if you did nothing but rest — the energy that keeps your heart beating, lungs breathing, and cells working. It is the largest single part of most people's daily energy use.

TDEE (Total Daily Energy Expenditure) is your BMR plus everything else you do: walking, working, exercising, even digesting food. It represents the total calories you actually use in a day. You get TDEE by multiplying your BMR by an activity factor. Because almost nobody spends the whole day at complete rest, your TDEE is always higher than your BMR — often by 20% to 90%, depending on how active you are. When people ask "how many calories should I eat a day," TDEE is the number they are really looking for.

The Mifflin-St Jeor Formula

The app calculates BMR using the Mifflin-St Jeor equation, which is widely regarded as one of the most accurate BMR estimates for the general population. It uses your weight, height, age and sex, with separate formulas for men and women:

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

Worked example: a 30-year-old woman weighing 65 kg at 165 cm. That is (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031.25 − 150 − 161 = about 1,370 kcal/day at rest. This is where sex genuinely changes the result — unlike BMI, the BMR formula has different constants for men and women, and it factors in your age. The app runs this calculation for you the moment you enter your details on the BMR tab.

The Five Activity Levels (TDEE Multipliers)

To turn BMR into TDEE, you multiply by an activity factor. The app offers five commonly used levels:

• Sedentary (little or no exercise): BMR × 1.2
• Lightly active (light exercise 1–3 days/week): BMR × 1.375
• Moderately active (moderate exercise 3–5 days/week): BMR × 1.55
• Very active (hard exercise 6–7 days/week): BMR × 1.725
• Extremely active (very hard exercise or a physical job): BMR × 1.9

Continuing the example above, our 1,370 kcal BMR at a moderately active level (× 1.55) gives a TDEE of roughly 2,120 kcal/day. Choose the level that honestly reflects a typical week — most people overestimate, so if you are unsure, pick the lower option.

Maintenance vs a Moderate Deficit

Once you know your TDEE, using it is straightforward in principle. To maintain your current weight, aim to eat roughly your TDEE in calories. To lose weight gradually, a commonly cited approach is a moderate deficit of about 500 kcal per day below your TDEE, which corresponds to a slow, sustainable rate of loss for many people. To gain weight, you would eat above your TDEE.

These are general guidelines, not personal prescriptions. Real calorie needs vary with metabolism, body composition, health conditions and medication, and very low intakes can be harmful. Do not drop below the calorie levels a health professional considers safe for you. The app shows your BMR and TDEE clearly so you have a reliable starting point, but the numbers are a guide to inform a conversation, not a diet plan on their own.

This guide is for general information only and is not medical advice — consult a doctor or a registered dietitian before making weight-loss or calorie decisions.