Calculate Your Daily Calories
Targets Based on Your Goal
Understanding Your Results
BMR (Basal Metabolic Rate)
This is the energy your body burns just to stay alive - breathing, circulating blood, maintaining organs, regulating temperature. It's what you'd burn lying in bed doing absolutely nothing for 24 hours.
BMR typically accounts for 60-75% of your total daily energy expenditure.
TDEE (Total Daily Energy Expenditure)
This is your BMR multiplied by your activity level. It's the total calories you burn in a day including all movement, exercise, and the thermic effect of food.
This is your maintenance level - eat this much and your weight stays stable. Eat less for weight loss, more for weight gain.
How Accurate Is This?
Honest answer: it's an estimate. The Mifflin-St Jeor equation is the most accurate formula we have for predicting BMR (within about 10% for most people), but individual variation exists.
Factors this calculator can't account for:
- Muscle mass - More muscle = higher metabolism. Two people at the same weight can have very different BMRs.
- Genetics - Metabolic efficiency varies between individuals.
- Hormones - Thyroid function, menstrual cycle, stress hormones all affect metabolism.
- NEAT variation - Some people fidget, move, and burn significantly more through daily activity than others.
- Metabolic adaptation - If you've been dieting, your actual TDEE may be lower than calculated.
Use It as a Starting Point
These numbers give you a sensible place to start. Track your weight for 2-3 weeks eating at your calculated target. If weight moves up or down when you expected stability, adjust by 100-200 calories and reassess. Your body tells you the truth; the calculator gives you the hypothesis.
The Maths Behind It
This calculator uses the Mifflin-St Jeor equation, published in 1990 and validated as more accurate than older formulas like Harris-Benedict:
Mifflin-St Jeor Formula
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
TDEE = BMR × activity multiplier
Setting Your Target
Once you know your maintenance calories:
- For weight loss: Subtract 300-500 calories for a sustainable 0.5-1lb (0.25-0.5kg) weekly loss
- For muscle gain: Add 200-300 calories to support muscle growth without excessive fat gain
- For maintenance: Eat at your TDEE and monitor weight stability
Larger deficits can work short-term but often backfire - increased hunger, metabolic adaptation, and loss of muscle mass. Patience and consistency beat aggressive restriction.
Key Takeaway
Your calorie target is a starting estimate, not a law of physics. Use the calculator to get in the right ballpark, then adjust based on how your body actually responds. Track consistently, be patient, and let real-world results guide your adjustments.
References
- Mifflin, M.D. et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition
- Frankenfield, D. et al. (2005). Comparison of predictive equations for resting metabolic rate. Journal of the American Dietetic Association
- Hall, K.D. et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet
- Trexler, E.T. et al. (2014). Metabolic adaptation to weight loss. Journal of the International Society of Sports Nutrition
