Calorie Calculator

BMR vs TDEE — two numbers, not one

Most people ask for “how many calories should I eat”, but there are really two answers.

• BMR (basal metabolic rate) is what your body burns at complete rest — keeping your heart beating, lungs breathing and cells running. It is the floor, the calories you would spend lying in bed all day. It usually accounts for 60-70% of total burn.
• TDEE (total daily energy expenditure) is BMR plus everything you do on top: walking, working, training, even fidgeting. This is your maintenance number — eat this and weight holds steady.

Every goal target is built off TDEE, never off BMR. Eating at BMR while you are active would create a large, often unsafe deficit.

The calculation chain

1. BMR via Mifflin-St Jeor:
   • Men: BMR = 10·kg + 6.25·cm − 5·age + 5
   • Women: BMR = 10·kg + 6.25·cm − 5·age − 161
2. TDEE = BMR × activity factor (1.2 sedentary → 1.9 extremely active)
3. Goal calories = TDEE ± deficit/surplus

How activity level changes the answer

The activity multiplier often moves the result more than age or height do. Two people with the same BMR can have very different needs:

Most people overestimate here. When in doubt, pick the lower band and adjust after two weeks of real-world data.

Goal presets

The calculator uses fixed daily adjustments because they are easy to apply and audit against your weight trend:

If a loss target would drop below the safety floor, the page clamps it and marks it with an asterisk.

Macro split

The macro cards use a general maintenance split: 30% protein, 40% carbohydrate and 30% fat. Protein and carbohydrate are converted at 4 kcal per gram; fat at 9 kcal per gram. Treat it as a practical starting point, not a prescription:

• Raise protein if you are dieting, lifting hard or prefer higher satiety.
• Raise carbohydrates if you do endurance training or perform better with more training fuel.
• Raise fats if that fits your food preferences, while keeping calories consistent.

Reality check

• Measured calorie burn can differ ±20% from the estimate — metabolism, NEAT (fidgeting), and tracker inaccuracy all add noise.
• Weight also shifts from water and glycogen short-term. Judge results over 2-3 weeks of daily weighing, not day-to-day.
• Recalculate every 4-5 kg of loss or gain. The formula uses current weight; as you get lighter, maintenance drops.

Safe deficits (and why crash diets backfire)

A sensible deficit is 15-25% below TDEE, which is roughly 250-750 kcal/day for most people and produces 0.25-0.75 kg of loss per week. That range is large enough to see progress but small enough to keep energy, training and muscle intact.

Crash diets — eating far below your needs — feel faster but usually cost you more than they give:

• You lose muscle, not just fat. Without enough protein and a gentle deficit, the body breaks down lean tissue, which lowers your BMR and makes maintenance harder later.
• Metabolic adaptation kicks in. The body defends itself by burning less (less fidgeting, lower body temperature, reduced NEAT), so the deficit shrinks on its own.
• Hunger and adherence collapse. Very low calories drive cravings, poor sleep and binges, and most of the lost weight returns once normal eating resumes.

Safety floor

Don’t drop below ~1,500 kcal/day for men or ~1,200 kcal/day for women without medical supervision. Below those levels, lean mass loss accelerates and hormonal disruption is common. The goals table on this page clamps to these floors automatically and flags any row that hits them.