How to Calculate Your BMR and Daily Calorie Target with the Mifflin-St Jeor Formula
Learn how to turn your weight, height, age and activity level into a BMR, a maintenance calorie figure and weight loss or gain targets.
BMR & Calorie Calculator
Introduction
Basal Metabolic Rate is the number of calories the body burns at complete rest, and it is the starting point for any calorie plan. The BMR & Calorie Calculator applies the Mifflin-St Jeor equation to your measurements, multiplies the result by an activity factor to estimate Total Daily Energy Expenditure (TDEE), and shows ready-made calorie targets for losing or gaining roughly 0.5 kg per week. Everything is calculated in the browser as you move the sliders.
Step-by-Step Instructions
- Select Gender using the Male or Female buttons, since the formula uses a different constant for each.
- Drag the Body Weight slider to your weight in kilograms (range 40 to 160 kg).
- Drag the Height slider to your height in centimetres (range 130 to 220 cm) and the Age slider to your age (15 to 80 years).
- Pick a Daily Activity Level from the dropdown: Sedentary, Light Exercise (1-3 days/week), Moderate Exercise (3-5 days/week) or Heavy Exercise (6-7 days/week).
- Read the Basal Metabolic Rate (BMR) and Daily Maintenance Calorie Target (TDEE) cards, then use the Weight Loss or Muscle Gain figures as your daily intake goal.
Key Use Cases
- Cutting Phase Planning: Set a daily intake 500 kcal below TDEE to lose about half a kilogram per week.
- Lean Bulk Target: Use the Muscle Gain figure (TDEE plus 500 kcal) as a ceiling when adding mass.
- Activity Comparison: Switch between Sedentary and Heavy Exercise to see how much training changes maintenance calories.
Frequently Asked Questions
Which formula does the calculator use?
It uses the Mifflin-St Jeor equation: 10 x weight (kg) + 6.25 x height (cm) - 5 x age, plus 5 for men or minus 161 for women. The result is rounded to the nearest whole calorie before it is displayed.
How are the Weight Loss and Muscle Gain numbers calculated?
The tool takes your TDEE and subtracts 500 kcal for the Weight Loss target or adds 500 kcal for the Muscle Gain target. A 500 kcal daily deficit or surplus corresponds to roughly 0.5 kg of change per week, which is the label shown on each card.
What activity multipliers are available?
The dropdown offers four factors: 1.2 for Sedentary, 1.375 for Light Exercise, 1.55 for Moderate Exercise and 1.725 for Heavy Exercise. TDEE is simply BMR multiplied by the selected factor, and there is no separate option for athletes training twice a day.