Protein calculator: understand a weight-based estimate

The result is arithmetic, not a prescription

The basic calculation multiplies a weight in kilograms by a factor in grams per kilogram. At an illustrative 80 kg and 1.2 g/kg, the result is 96 g per day. Selecting 1.4 gives 112 g. These are worked examples, not a judgement that either target is right for a particular person.

The British Nutrition Foundation gives 0.75 g/kg as the UK adult reference intake. A reference intake describes a population basis; health, age and the circumstances of weight loss can change the question a dietitian needs to answer. [1]

The default factor is displayed so that it can be changed and understood. It is not selected from a medical assessment, and the tool does not ask for the information needed to perform one.

Actual, reference and adjusted weight

Using current body weight is the simplest calculation. At a higher body weight, multiplying the full mass by a high factor may produce an amount that is inappropriate or difficult to achieve. A 2025 joint professional advisory describes the uncertainty over using actual, corrected or lean weight during GLP-1 treatment. It does not establish one universally correct formula. [2]

The reference options require height and the formula coefficient. They do not silently assume a height. Adjusted weight is rejected when actual weight is at or below the reference value. Choose a method with a dietitian when the distinction matters; do not simply choose whichever produces the most appealing number.

The height formula is defined in the cited protocol; that source is used only for its arithmetic definition, not as a protein-intake guideline. The adjustment percentage here remains an explicit modelling assumption. [3]

What the selectable factors mean

The tool offers 0.75, 1.0, 1.2, 1.4 and 1.6 g/kg so you can inspect the effect of different assumptions. The joint advisory discusses proposed ranges such as 1.2–1.6 g/kg during active weight reduction, while noting uncertainty over the weight basis and the need for individual assessment. [2]

Higher numbers should not automatically be read as better. A nutritious diet also needs enough energy, carbohydrate, fibre, fat and micronutrients. A protein total cannot show whether someone is eating enough overall or tolerating treatment. A result that seems unmanageable is a reason to seek advice, not to force food or supplements.

Regular muscle-strengthening activity and adequate nutrition are considered together in the advisory. Increasing protein without a suitable activity plan does not by itself establish that muscle will be preserved. [2]

Units, rounding and a practical food plan

Enter weight in kilograms, pounds, or whole stone plus extra pounds. Switching units converts the same underlying mass; it should not reinterpret 80 kg as 80 lb. The display is rounded, while the calculation retains the value in kilograms. Feet and inches are entered separately when a reference-weight method needs height.

The estimated grams are rounded to a whole number. The three-meal figure simply divides that estimate into three parts. It is not an absorption limit or a rule that every meal must contain exactly the same amount.

Once a suitable target has been agreed, use food labels and realistic portions to understand how to meet it. Beans, lentils, eggs, fish, dairy foods, tofu and other foods can contribute. Supplements are not automatically required. [1]

When to use individual nutrition advice

This tool is for adults exploring arithmetic. It is not suitable for setting diets in pregnancy, breastfeeding, childhood, kidney or liver disease, an eating disorder, or a condition requiring specialist nutrition. Its working bounds are input checks, not medical eligibility thresholds.

Seek help if appetite reduction makes normal eating difficult, symptoms interfere with drinking, or weight is changing unexpectedly. A prescriber can assess the medicine and a registered dietitian can assess the food plan. The side-effects guide explains symptoms that need urgent attention.

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