The number of calories the body needs to keep all organs functioning normally when at rest. It is given as a calories per day figure.

There are several factors which can affect BMR, including gender, BMI and age.

The formulae to calculate BMR is as follows:

For women:

655.1 + (9.6 x weight in kilos) + (1.8 x height in centimetres) - (4.7 x age in years)

For men:

66.47 + (13.7 x weight in kilos) + (5 x height in centimetres) - (6.8 x age in years)

So, for a man aged 30, who is 180 centimetres tall and weighs 65 kilograms, this would be:

66.47 + (13.7 x 65) + (5 x 180) - (6.8 x 30) = 1653 calories per day.