Updated June 8, 2026 · 12 min read
Written by Muhammad Abdullah Rauf · Founder, EverydayTools.pro
Calculating calories for weight loss sounds complicated — but it comes down to one equation: eat fewer calories than you burn. The challenge is knowing exactly how many calories you burn (your TDEE) and how large a deficit you should create. This guide walks you through the complete calculation from scratch, using the best available formula (Mifflin-St Jeor), validated activity multipliers, and evidence-based deficit targets.
Medical disclaimer
Calorie calculations are estimates. Individual requirements vary by metabolic health, medications, age, and hormonal factors. Consult a registered dietitian or physician before making significant dietary changes, especially if you have a medical condition.
Step 1: Calculate Your BMR (Basal Metabolic Rate)
Your BMR is the number of calories your body burns at complete rest — just to maintain organ function, breathing, and body temperature. It accounts for 60–75% of total daily calorie burn for sedentary people.
The Mifflin-St Jeor equation is the gold standard for BMR estimation. A 2005 study in the Journal of the American Dietetic Association found it to be the most accurate of common formulas, within ±5–8% of measured BMR for most adults.
/* Mifflin-St Jeor BMR 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
Example (30-year-old woman, 65 kg, 165 cm):
BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031 − 150 − 161 = 1,370 kcal/day
Step 2: Calculate Your TDEE (Total Daily Energy Expenditure)
Your TDEE is your BMR multiplied by an activity factor. This is your true maintenance calorie level — the number of calories you need to eat to hold your current weight.
| Activity Level | Multiplier | Who It's For |
|---|---|---|
| Sedentary | BMR × 1.2 | Desk job, no exercise |
| Lightly active | BMR × 1.375 | Light exercise 1–3 days/week |
| Moderately active | BMR × 1.55 | Exercise 3–5 days/week |
| Very active | BMR × 1.725 | Hard training 6–7 days/week |
| Extra active | BMR × 1.9 | Physical job + intense daily training |
Continuing the example: BMR = 1,370 kcal × 1.375 (lightly active) = 1,884 kcal/day TDEE.
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Our Calorie Calculator does all of this automatically — enter your details and select your goal to get your personalised TDEE and deficit target instantly, in your browser.
Step 3: Create a Calorie Deficit
To lose fat, you need to eat fewer calories than your TDEE. The size of your deficit determines how fast you lose weight:
| Strategy | Daily Deficit | Weekly Loss | Risk |
|---|---|---|---|
| Mild cut | −250–300 kcal | ~0.25 kg (0.5 lb) | Very low |
| Moderate (recommended) | −500 kcal | ~0.5 kg (1 lb) | Low |
| Aggressive cut | −750–1000 kcal | 0.75–1 kg (1.5–2 lb) | Medium |
| VLCD | >1000 kcal | >1 kg | High — medical supervision |
For our example: target calories = 1,884 − 500 = 1,384 kcal/day for approximately 0.5 kg/week weight loss.
Important floor limits: Never eat below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. Below these levels, nutrient deficiencies and significant muscle catabolism become likely.
Step 4: Set Your Protein Target
Total calories drive weight loss, but protein intake determines whether you lose fat or muscle. A high-protein diet during a calorie deficit:
- Preserves muscle mass (critical for long-term metabolism)
- Increases satiety (reduces hunger and cravings)
- Has the highest thermic effect of food (~25–30% of calories burned in digestion)
Evidence-based target: 1.6–2.2 g of protein per kg of body weight per day. For a 65 kg person, that's 104–143 g of protein daily.
Use our protein intake calculator to find your personalised target based on weight, goal, and activity level.
Step 5: Track Progress and Adjust
Calorie calculations are estimates. You need to monitor actual results and adjust:
- Weigh yourself weekly — same day, same time (morning, after bathroom). Use a 7-day average to reduce noise from water fluctuations.
- If no weight loss after 2 weeks, reduce calories by 100–200 kcal/day and reassess after another 2 weeks.
- Recalculate every 5–10 kg lost. As your body weight decreases, so does your TDEE — your calorie target must be updated.
- Watch for plateaus. After 8–12 weeks of dieting, metabolic adaptation can reduce your TDEE by 100–400 kcal/day. A 2-week "diet break" at maintenance calories can reset this.
Common Calorie Calculation Mistakes
Overestimating exercise calorie burn
Fitness trackers overestimate burn by 20–90%. Don't "eat back" exercise calories separately — use the activity multiplier in your TDEE instead.
Not accounting for liquid calories
Coffee drinks, juices, alcohol, and smoothies can add 200–800 kcal/day invisibly. Track all beverages.
Using the same calorie target for months
Your TDEE decreases as you lose weight. A target set for 80 kg is too high once you're at 70 kg. Recalculate every 5–10 kg.
Choosing too aggressive a deficit
A >1,000 kcal/day deficit accelerates muscle loss, increases fatigue, and often leads to bingeing and rebound. Slow and steady typically outperforms crash dieting over 3–6 months.
Quick Reference: Full Calculation Example
// Example: 30-year-old woman, 65 kg, 165 cm, lightly active
// Step 1: BMR (Mifflin-St Jeor)
BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 1,370 kcal
// Step 2: TDEE (lightly active = ×1.375)
TDEE = 1,370 × 1.375 = 1,884 kcal
// Step 3: Weight loss target (−500 kcal/day)
Target = 1,884 − 500 = 1,384 kcal/day
// Step 4: Protein target
Protein = 65 kg × 1.8 g/kg = 117 g/day
Frequently Asked Questions
How many calories should I eat to lose weight?
Eat your TDEE minus 500 kcal/day for ~0.5 kg/week loss. Calculate your TDEE using BMR × activity multiplier. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men).
How accurate is the Mifflin-St Jeor equation?
Within ±5–8% of measured BMR for most normal-weight adults. Less accurate for very lean athletes (use Katch-McArdle with body fat %) or severely obese individuals.
Is a calorie deficit the only way to lose weight?
Mechanistically yes — fat loss requires an energy deficit. But you can create this deficit by eating less, moving more, or both. Diet changes are typically more effective than exercise alone for creating a sustained deficit.
Does it matter what I eat, or just calories?
For weight loss, total calories are primary. For body composition (fat vs muscle) and health, food quality matters: high protein preserves muscle, fibre promotes satiety, and processed foods promote overconsumption.
Why am I not losing weight in a calorie deficit?
Common reasons: underestimating calories eaten (especially from oils, sauces, drinks), overestimating exercise burn, water retention masking fat loss, metabolic adaptation, or hormonal factors. Reweigh every 7 days and look at the trend over 4+ weeks.
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Enter your details once and get your personalised BMR, TDEE, and calorie target in seconds. Runs entirely in your browser — no signup, no data upload.
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