Calorie Calculator

Last updated: September 2, 2026 · Calsify Editorial Team · Verified formula

BMR and TDEE Explained

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just to maintain vital functions like breathing, circulation and cell maintenance. Think of it as your body's idle fuel consumption.

Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor — the total calories you burn accounting for your actual movement and exercise. TDEE is the number that matters most for diet planning.

To lose weight: eat below your TDEE (a deficit of 300-500 calories/day creates sustainable loss of 0.5-1 lb/week)
To maintain weight: eat at your TDEE
To gain muscle: eat above your TDEE with adequate protein and resistance training

The Mifflin-St Jeor Formula

Our calculator uses the Mifflin-St Jeor equation (Mifflin MD, St Jeor ST, et al., 1990), which is validated as the most accurate formula for estimating BMR in non-obese adults and is the equation currently recommended by the Academy of Nutrition and Dietetics as the preferred method for calculating calorie needs:

Formula

Men: BMR = 10×Weight(kg) + 6.25×Height(cm) − 5×Age + 5
Women: BMR = 10×Weight(kg) + 6.25×Height(cm) − 5×Age − 161

TDEE = BMR × Activity Multiplier: • Sedentary (desk job, little exercise): × 1.2 • Lightly active (1-3 days/week exercise): × 1.375 • Moderately active (3-5 days/week): × 1.55 • Very active (6-7 days/week hard exercise): × 1.725 • Extra active (physical job + hard exercise): × 1.9

Macronutrients and Calorie Quality

Calories tell you quantity — macronutrients tell you quality. For most health and fitness goals, the composition of your calories matters as much as the total count:

Protein: 4 calories/gram. Essential for muscle maintenance, satiety, and immune function. Aim for 0.8-1.6g per kg of body weight depending on activity level.

Carbohydrates: 4 calories/gram. Primary fuel for high-intensity exercise and brain function. Focus on complex carbs (whole grains, vegetables, legumes) over simple sugars.

Fat: 9 calories/gram. Essential for hormone production, vitamin absorption and satiety. Prioritise unsaturated fats (olive oil, nuts, avocado) over saturated and trans fats.

For weight loss, higher protein intake (1.2-1.6g/kg) preserves muscle mass while creating a calorie deficit — preventing the metabolic adaptation (slowing metabolism) that occurs with low-protein calorie restriction.

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Pro Tip: TDEE calculators are estimates — your actual needs may vary by 10-15%. The best approach: calculate your TDEE, eat at that level for 2 weeks, and adjust up or down by 100-200 calories based on what your weight does. Body feedback beats any formula.

Calorie Calculator: Interpretation Framework

Treat the answer as a planning signal and validate it against your real constraints. For calorie calculator, the core objective is screening-level insights and healthy trend tracking. Input quality directly controls output quality, so verify each field carefully. calculator output is not a diagnosis and must be interpreted with clinical context. Key intent phrases for this page: calorie calculator, daily calorie calculator, tdee calculator, bmr calculator.

Run a three-scenario matrix (baseline / conservative / stress) and compare result stability. If outcomes diverge widely, your decision is assumption-sensitive and needs a larger safety margin. If outcomes remain close, confidence in your plan increases. For cross-validation, compare your outcome with related tools such as BMI Calculator, Ideal Weight Calculator, Body Fat Calculator.

Input Quality Checklist for Calorie Calculator

Use this checklist before trusting the final output:

1. Enter age, gender, height and weight: Fill in your personal details for an accurate BMR calculation.
2. Select activity level: Choose your daily activity level from sedentary to very active.
3. Select your goal: Pick weight loss, maintenance or weight gain.
4. Click Calculate: See your BMR, TDEE and recommended daily calorie intake for your goal.

After calculation, verify that the result is logically consistent with your own constraints, timeline, and risk tolerance. re-check when your measurements, goals, or activity level changes. This is especially important for high-impact decisions where a small input error can produce a large planning gap.

Frequently Asked Questions

How many calories should I eat to lose 1 kg per week?

One kilogram of body fat contains approximately 7,700 calories. To lose 1 kg per week, you need a daily calorie deficit of approximately 1,100 calories (7,700 ÷ 7). For most people, this extreme deficit is difficult to sustain and may cause muscle loss. A safer target is 0.5 kg/week, requiring a 550-calorie daily deficit — more sustainable and better for long-term results.

Why do I stop losing weight even when eating at a deficit?

This is called a weight loss plateau and has two common causes. First, as you lose weight, your TDEE decreases — your calorie needs fall as you become lighter. Recalculate your TDEE with your current weight. Second, metabolic adaptation: prolonged calorie restriction can reduce metabolic rate. Periodic diet breaks (eating at TDEE for 1-2 weeks) can help reset the metabolism before resuming the deficit.

Is it safe to eat 1,200 calories per day?

1,200 calories is considered a minimum threshold for women (1,500 for men) to get adequate nutrients. Below this, it becomes very difficult to meet micronutrient needs without supplementation, and metabolic adaptation becomes significant. Very low calorie diets (VLCDs) below 800 calories should only be done under medical supervision. For sustainable results, a moderate deficit of 300-500 calories below TDEE is preferred.

Do I need to count calories to lose weight?

No, but calorie awareness helps. Some people lose weight effectively through food quality changes (cutting processed food, added sugar and refined carbs) without explicit counting. Others need precise tracking to create a consistent deficit. If your weight is not moving in the desired direction after 4-6 weeks of conscious effort, tracking calories for a few weeks provides valuable insight into where the imbalance lies.

How accurate are fitness tracker calorie burn estimates?

Fitness trackers estimate calorie burn from heart rate and movement data — they typically overestimate energy expenditure by 20-30%, sometimes more. Do not "eat back" all exercise calories displayed by your tracker, as this often eliminates the deficit you created. Use tracker data as a relative indicator (more movement = more burn) rather than absolute calorie numbers.

How do I improve reliability when using the Calorie Calculator?

Start with verified inputs, run at least three scenarios, and compare the full breakdown instead of only the headline number. Then re-run after any material assumption change so your decision stays aligned with current data.

What should I do after I get a result from the Calorie Calculator?

For cross-validation, compare your outcome with related tools such as BMI Calculator, Ideal Weight Calculator, Body Fat Calculator. Use the result to shortlist options, then confirm final numbers using official statements, current rates, or professional guidance relevant to your category.