Category: Guides

Body mass index (BMI) is a simple ratio of your weight to your height: weight in kilograms divided by height in metres squared. It is popular because it is quick, free and easy to compare across large groups of people.

The standard BMI ranges

For adults, the commonly used ranges are: under 18.5 is underweight, 18.5 to 24.9 is the normal range, 25 to 29.9 is the overweight range, and 30 or above is the obesity range.

What BMI cannot tell you

BMI does not distinguish between muscle and fat, and it says nothing about where fat is stored. A muscular athlete can land in the overweight range while being very healthy, and someone with a normal BMI can still carry excess body fat. That is why it works best as a starting point, alongside measures such as waist-to-hip or waist-to-height ratio.

Try it yourself

Enter your height and weight below to see your BMI and how far you are from the edges of the healthy range.

This calculator is an educational estimate, not medical advice. Talk to a qualified professional before making health decisions.

Your Total Daily Energy Expenditure (TDEE) is an estimate of how many calories you burn in a typical day, including exercise and everyday movement. It is the foundation of any sensible plan to lose, maintain or gain weight.

How it is calculated

First, your basal metabolic rate (BMR) is estimated from your weight, height, age and sex using the Mifflin-St Jeor equation. Then that number is multiplied by an activity factor, from 1.2 for a sedentary lifestyle up to 1.9 for very hard daily training.

Using your TDEE

Eating around your TDEE tends to maintain your weight. A modest deficit below it is commonly used for fat loss, and a modest surplus above it for gaining muscle. Small, steady changes are easier to sustain than aggressive ones.

Calculate yours

Treat the result as a starting point and adjust based on how your body responds over a few weeks.

Macronutrients, or macros, are the three main nutrients that supply your calories: protein, carbohydrate and fat. Tracking them is a more precise way to eat than counting calories alone.

What each macro does

Protein (4 calories per gram) supports muscle repair and keeps you feeling full. Carbohydrate (4 calories per gram) is your body’s preferred fuel for training. Fat (9 calories per gram) supports hormones and absorbs vitamins.

A sensible starting point

A common starting target for active people is around 1.6 to 2 grams of protein per kilogram of body weight, then fat at a moderate level, with the remaining calories coming from carbohydrate.

Get your numbers

These figures are educational estimates. Individual needs vary, so consult a qualified professional for personal advice.