How it works
This calculator uses the Mifflin-St Jeor equation, the most widely validated formula for estimating resting metabolic rate in adults. First it calculates your basal metabolic rate (BMR), the calories you would burn lying still all day. Then it multiplies BMR by an activity factor to estimate total daily energy expenditure (TDEE).
The equations are:
- Men:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) + 5 - Women:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) − 161
Activity multipliers range from 1.2 for a sedentary lifestyle to 1.9 for very heavy daily training or a physical job. These multipliers are approximations; the exact calories burned from walking, standing, fidgeting, and structured exercise vary from person to person.
The cut and bulk targets add or subtract fixed amounts. A 500-calorie daily deficit is a common starting point for fat loss, while a 300-calorie surplus is conservative for muscle gain. In practice, your best target is the one you can follow consistently while tracking real-world changes in weight, energy, and performance for at least two to four weeks.
Limitations
All BMR equations are estimates. They do not account for muscle mass, hormones, sleep quality, medications, medical conditions, or individual metabolic adaptation. Use the result as a starting point, then adjust based on measured outcomes.