Calorie Calculator

How to use

1. Enter age, weight and height, and pick the activity level that matches an average week.
2. Read maintenance first — the figure that holds your weight steady.
3. Choose a goal to see the target for that rate of change.
4. Switch the macronutrient split to see the same target as grams of protein, carbohydrate and fat.

Features

• Mifflin-St Jeor for resting energy, the formula that has held up best against measurement in the general population.
• Maintenance from the standard activity multipliers, with each multiplier shown so nothing is hidden.
• Targets derived from a real rate — 0.5 kg a week is 550 kcal a day, not a round number someone picked.
• Never prints a target below the floor for an unsupervised diet, and says when it had to raise one.
• Metric and imperial, converted internally so both answer identically for the same body.

Frequently asked questions

How accurate is this?

It is a population average. Measured against a metabolic cart, Mifflin-St Jeor lands within about 10% for most people, which on a 2,000 kcal maintenance is a couple of hundred kilocalories either way. Use it as a starting point, hold it for two or three weeks, and adjust from what the scale actually does — that feedback beats any formula.

Why does it only offer male and female?

Because the formula was published with exactly two constants, one for each group it was fitted on, and the difference between them is a single number at the end of the sum. There is no third constant to offer that would not be invented. If neither fits you, run both and read the range they give as the range.

Why was my target raised?

Because the deficit you asked for took it below the level at which food stops covering basic nutrition — roughly 1,200 kcal for women and 1,500 for men without supervision. The arithmetic would happily print a lower number; a tool that does is giving harmful advice. Choose a slower rate, or add activity instead of removing food.

Where does 7,700 kcal per kilogram come from?

It is the energy stored in a kilogram of body tissue, and it is what every weekly rate in every calculator is derived from. It is also an approximation: the body adapts to a deficit, so real loss slows over months. Expect the first weeks to track the estimate and later ones to lag it.

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