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Energy & Nutrition

Calorie, BMR, TDEE, macro, protein, and water intake calculators — how much fuel and hydration your body needs.

Six calculators covering how much fuel your body needs and what to build it from. They stack: basal rate, then total daily expenditure, then a goal-adjusted target, then how to split it.

The order matters. Each one takes the previous number as its starting point, and the most common mistake in this category is picking a target from the middle of that chain without the one before it.

How these fit together

Four of these six are the same calculation at different stages. Knowing which stage you are at prevents the two errors that make a plan fail before it starts: eating at your BMR, and double-counting exercise.

The chain from resting metabolism to a daily plan.
StepCalculatorWhat it adds
1BMRWhat you burn at complete rest — usually 60–70% of the total
2TDEEMultiplies BMR by activity to get your maintenance level
3CalorieApplies your goal — a deficit, maintenance or a surplus
4MacroSplits that target into protein, carbohydrate and fat

Never eat at your BMR

It is the most consequential mistake in this category. BMR is what you would burn spending the whole day unconscious and motionless. Eating at it while living a normal life creates a very large deficit, with the muscle loss and nutrient shortfalls that follow. Start from TDEE.

What is well-founded and what is a judgement call

It is worth knowing which half of your calorie target is science and which half is an assumption, because they have very different error bars.

  • The BMR equation is validated. Mifflin-St Jeor was derived from indirect calorimetry and predicts resting rate within 10% for around 70% of people.
  • The activity multiplier is a guess. The gap between sedentary and very active exceeds 500 kcal a day, which is the same size as the deficit most people want. Most people choose too high.
  • Protein has an evidence-based target. It is the one macro where the amount genuinely changes body composition rather than just the arithmetic.
  • The carb-to-fat ratio barely matters for weight. Two large randomised trials found no meaningful difference between splits at matched calories. Pick what you can eat.

Recalculate as you go

A smaller body needs fewer calories. The target that worked at the start creates a smaller deficit five kilograms later, purely by arithmetic. Recalculating every 4–5 kg is the step almost everyone skips and the most common reason a plan quietly stops working.

Frequently asked questions

TDEE, always. BMR is only the resting component and eating at it would put you in a severe deficit. TDEE is BMR multiplied by your activity level, and it is the maintenance figure any goal should be set against.

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