Body Mass Index Calculator

Enter height and weight and check if you are “overweight”..

Weight : kg

height : m

Formula for body mass index (BMI). $$BMI = \frac{mass (kg)}{height (m)^2}$$

Guidelines for Normal BMI

“Normal” BMI is between 18.5 and 25 for adults.1)
⇒ <18.5 is underweight
⇒ >25 is overweight
⇒ >30 is obese

BMI by country

For children, normal BMI varies with age. Below is a chart for boys2):

Gaining / Loosing Weight

How many calories do I burn per day doing nothing?

Basal Metabolic Rate3) is the minimum energy expenditure of endothermic animals at rest. This is the baseline for the calorie intake you need to maintain your weight.

This can be estimated using the Mifflin St Jeor Equation (1990)4):
P = 10.0 m + 6.25 h - 5.0 a + s

P = total heat production at complete rest, kcal/day
m = mass in kg
h = height in cm
a = age in years
where s is +5 for males and −161 for females

Weight : kg

height : m

age : years


Assuming male - subtract 166 kcal for female

How many calories should I consume per day?

Calories used through exercise come on top of the Basal Metabolic Rate (BMR) but may be less than you think. For example, walking 5000 steps only burns ~200 extra calories
A sedentary lifestyle is sometimes classified as walking <3000 steps/day and doing normal day to day tasks. A minimum of 150mins a week excercise is recomended although you are only doing damage limitation from age 385) onwards.

Typical recommendations for adult consumption is between 2000 and 3000 Cal / day 6)

What calorie reduction needed to achieve weight loss?

You need calorie deficit of 7000Cal to reduce 1kg in weight.
⇒ to loose 1k / week, you need to cut back 1000Cal/day (~half normal consumption!)

How many calories in different foods?

Small calorie (cal) is the energy needed to increase 1 gram of water by 1ºC at a pressure of 1 atmosphere.

kcal = Cal

1 kilocalorie = 4.2 kilojoules

  • 1 cube of sugar ~9 Cal
  • 1 medium egg ~70 Cal
  • 1 potato - 160 Cal
  • 1 slice of pizza 285 Cal
  • 500ml beer 200…250 Cal

Alcohol consumption

1 Unit of Alcohol = 10ml of pure Alcohol

For a given Drink
Volume (l) x % Alcohol = units
Typical Beer
0,5 * 4 = 2 units

1g = 7 calories (1ml = 0,8g alchohol)
⇒ 1 unit = 56 calories ⇒ 2 units = 112 calories


Men should drink no more than 21 units of alcohol per week, no more than four units in any one day, and have at least two alcohol-free days a week.

  • 1 Promille = 1 Gramm Alkohol/ pro 1 Kilogramm Blut
  • 0,5 Promille is current limit blood alcohol limit in Germany/Ireland 7)

Rough calculation with assumptions

  • All alcohol instantly absorbed into blood and no time to metabolise is away.
  • Men have 70% of body weight as fluid

For 75kg man ⇒ ~ 50kg. 1 500ml beer with $5\%$ alcohol content has ~25g pure alcohol $$Blood \mbox{ } Alcohol \mbox{ } Content = \frac{2.5\cdot10^{-3}}{50} = 0,5 \cdot10^{-3} = 0,5 \unicode{x2030} (permille)$$

Men can expect to metabolise 0.15…0,2 ‰ per hour. One beer will, in this case, keeps your system busy for 2-3 hours. Above 10‰ (1) is enough to put you on the "most recorded ever list"

Mifflin, MD; St Jeor, ST; Hill, LA; Scott, BJ; Daugherty, SA; Koh, YO (1990). “A new predictive equation for resting energy expenditure in healthy individuals”. The American Journal of Clinical Nutrition. 51 (2): 241–7
Irish Times 5th Dec 2016
calculate/body_mass_index.txt · Last modified: 2019/09/10 03:42 (external edit)
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