Calorie calculator

Three steps under the hood:

1. BMR via Mifflin-St Jeor (1990). The American Dietetic Association's 2005 systematic review found this the most accurate predictive equation for the general adult population — better than Harris-Benedict, Owen, or WHO/FAO/UNU.
2. TDEE = BMR × activity factor (PAL). 1.2 sedentary → 1.9 very active. Most people overestimate by one tier; pick the level that matches what you actually do, not what you aspire to.
3. Goal offset. Subtract for weight loss or add for gain: ±250 / ±500 / ±750 kcal/day for slow / standard / aggressive rates.

The 7700 kcal ≈ 1 kg fat rule (Wishnofsky, JAMA 1958) is the textbook starting point but overstates real-world fat loss — metabolism adapts down during a deficit, lean mass changes, and water/glycogen swings show up on the scale.

Sustainable rates are 0.5–1% of body weight per week:

• Mild (±250 kcal/day). Best for the last few kilos when you're already lean, or for people who historically rebound from sharp deficits.
• Standard (±500 kcal/day). Default for most adults. Tracks well with the textbook 0.5 kg / 1 lb per week.
• Aggressive (±750 kcal/day). Only when you have substantial fat to lose and good adherence skills. Harder to keep lean mass; expect more hunger.

For weight gain, slower is better: muscle accrues at roughly 0.25–0.5% body weight / week even with optimal training and protein intake. Eating more than that just adds fat.

The default 30 protein / 40 carbs / 30 fat split is a moderate-carb balanced template that works for most people. Tune it for context:

• Protein: 1.6–2.2 g/kg body weight is the evidence-based range for active adults (Morton et al. 2018 meta-analysis). Higher (2.4–2.8 g/kg) during aggressive cuts to protect lean mass.
• Fat: Don't go below 0.5 g/kg body weight for hormonal health. Most adults do well in the 0.7–1.2 g/kg range.
• Carbs: Whatever's left after protein and fat are set. Endurance athletes benefit from more (5–10 g/kg on training days). Sedentary adults can comfortably go lower.

Macros are computed by splitting the calorie target — 4 kcal/g for protein and carbs, 9 kcal/g for fat.

This tool refuses to recommend below 1500 kcal/day for men and 1200 kcal/day for women. Below those thresholds:

• Hitting micronutrient (vitamin/mineral) targets becomes hard or impossible without medical supervision.
• Muscle loss accelerates relative to fat loss, especially without resistance training.
• Resting energy expenditure adapts downward more sharply, making rebound weight gain after the diet easier.
• Bone density, immune function, hormone balance and mood all degrade under prolonged severe restriction.

If your maintenance TDEE is already low and even mild deficits push you under those floors, the right move is to raise TDEE through more activity rather than cutting calories further.