How This Calculator Works
This calculator uses the Mifflin-St Jeor equation, the gold standard for estimating calorie needs recommended by the Academy of Nutrition and Dietetics. Published in 1990, it has been validated against measured metabolic rates in dozens of studies and outperforms older formulas like Harris-Benedict for most adults.
The formula:
- Male BMR: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Female BMR: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Your TDEE is calculated by multiplying BMR by an activity factor (1.2 for sedentary up to 1.9 for extra active). Your final calorie target adjusts TDEE based on your goal: a 500 calorie/day deficit produces approximately 1 lb of weight loss per week.
Understanding Your Results
BMR (Basal Metabolic Rate) is the minimum calories your body needs just to stay alive — breathing, circulation, temperature regulation. You should never eat below your BMR long-term.
TDEE (Total Daily Energy Expenditure) is your maintenance calories — the number where your weight stays stable. Eat less and you lose weight; eat more and you gain.
The macro split shows a general 30% protein / 40% carbs / 30% fat distribution, which suits most people's goals. Athletes or people building muscle may want higher protein (use the Macro Calculator to customize).
How to Track Your Calories Accurately
Knowing your calorie target is only half the equation — you also need to track accurately. Research shows people underestimate their food intake by 30-50% when estimating portions. There are three main approaches:
- AI photo tracking (most convenient): Apps like PlateLens analyze a photo of your meal and calculate nutrition automatically within ±1.2% accuracy.
- Food scale + database (most accurate DIY): Weigh all food, log in a database. Takes 5-10 minutes per meal.
- Volume/portion estimation (least accurate): Prone to 30-50% errors, not recommended if you have specific goals.
Frequently Asked Questions
How many calories should I eat to lose weight?
A deficit of 500 calories per day relative to your TDEE typically produces about 1 lb (0.45 kg) of weight loss per week. This is the most sustainable rate for preserving muscle mass. Faster loss (2 lbs/week) is possible with a 1000-calorie deficit but requires strict adherence and carries higher risk of muscle loss.
What is BMR and why does it matter?
BMR is your body's baseline energy requirement at complete rest. It accounts for 60-75% of your total calorie burn. Understanding your BMR helps set the floor for safe eating — going below it for extended periods causes metabolic adaptation and muscle loss.
What is TDEE?
Total Daily Energy Expenditure is your maintenance level — where calorie intake equals output. It includes BMR plus thermic effect of food (~10%), non-exercise activity thermogenesis (NEAT), and deliberate exercise. Your TDEE is what the calculator shows before any goal adjustment.
How accurate are calorie calculators?
The Mifflin-St Jeor equation is accurate within 10% for most non-obese adults. Athletes and people with high muscle mass tend to have higher actual metabolisms. Treat your result as a starting point: track your weight for 2-4 weeks and adjust by 100-200 calories if results don't match predictions.
What is the best way to track calories?
AI-powered photo tracking (PlateLens) is the most convenient and accurate for most people, achieving ±1.2% accuracy without manual logging. For those who prefer manual tracking, weighing food with a kitchen scale and logging in a database is the next best option.
Should I eat back exercise calories?
It depends on your activity setting. If you selected "sedentary" but workout 4x/week, you should eat back 50-75% of exercise calories burned. If you selected your true activity level, exercise is already built in. The safest approach: use sedentary as your base and add exercise separately.
How often should I recalculate?
Every 5-10 lbs of weight change. As you lose or gain weight, your BMR changes — a common reason people hit plateaus. Recalculate every 4-6 weeks to keep your target accurate.
Is 1200 calories a day safe?
1200 calories is generally considered the minimum intake threshold for women to get adequate micronutrients. Men should not go below 1500 calories. Our calculator displays a warning if your calculated target falls below these thresholds.