Body Fat Calculator

Body fat formulas

Body fat percentage is a measure of body fitness and also an indicator of body shape. In order to assess your current body status indicators such as percentage of body fat, the lean body weight as well as two other weight and caloric indicators, the body mass index (BMI) and the basal metabolic rate (BMR) are crucial. 

The equations used for determining body fat percentage are those developed by the Naval Health Research Center by Hodgdon and Beckett in 1984.

• Body Fat Male = 495 / (1.0324 - 0.19077 x (Log(Waist - Neck)) + 0.15456 x (Log(Height))) - 450
• Body Fat Female = 495 / (1.29579 - 0.35004 x (Log(Waist + Hip - Neck)) + 0.22100 x (Log(Height))) - 450

The formulas for body mass index are:

• BMI = Weight (kg) / Height (m)2
• BMI = Weight (lbs) / Height (in)2 x 703

The BMR is obtained by the Harris-Benedict equations:

• BMR Male (kcal/day) (Metric) = 66.5 + (13.75 × Weight, kg) + (5.003 × Height, cm) - (6.775 × Age)
• BMR Female (kcal/day) (Metric) = 655.1 + (9.563 × Weight, kg) + (1.850 × Height, cm) - (4.676 × Age)
• BMR Male (kcal/day) (English) = 66 + (6.23 x Weight in lbs) + (12.7 x Height in inches) - (6.8 x Age)
• BMR Female (kcal/day) (English) = 655 + (4.35 x Weight in lbs) + (4.7 x Height in inches) - (4.7 x Age)

With the activity adjustments:

• Sedentary (little to no exercise) = BMR × 1.2
• Light exercise (1-3 days per week) = BMR × 1.375
• Moderate exercise (3–5 days per week) = BMR × 1.55
• Heavy exercise (6–7 days per week) = BMR × 1.725
• Very heavy exercise (twice per day, extra heavy workouts) = BMR × 1.9

Desirable body fat percentage

The American Council on Exercise advises the following ranges of general body-fat percentage categories:

Jackson & Pollock have devised guidelines of age and gender appropriate body fat percentages:

The importance of body fat

Body fat consists of two components, the essential body fat and the storage body fat, the first component being the one that maintains life and reproductive functions and is typically between 10 and 13% in females and 2 and 5% in males.

Storage fat accumulates in the adipose tissue in the form of either visceral fat (fat around organs in the abdominal cavity) or subcutaneous fat (under the skin and wrapped around vital organs).

The main purpose of the body fat (adipose tissue) is to deliver lipids that the body uses to generate energy. Body fat and its accumulation rate is influenced by food intake, exercise and genetic factors.

There are also gender specific differences in the way the female and male body stores fat (preponderantly around stomach in men and around buttocks and thighs in women).

Both excess and insufficient body fat can lead to detrimental health effects. Excessive body fat leads to a person becoming overweight or obese.

Some of the most common complications associated with obesity include reduction in quality of life, poorer mental health outcomes, obstructive sleep apnea and high mortality and morbidity risks from cardiovascular disease, stroke, type 2 diabetes or cancer.

Reducing body fat

Losing between 1 and 3% of the body fat percentage in a period of 30 days is considered achievable and healthy fat loss. It is important to note that reducing fat is not the same as reducing body weight and simply lowering caloric intake is not sufficient.

Some of the lifestyle changes you may want to consider when aiming to lose body fat include:

• Exercise: make a long-term plan starting from basic to then moderate and greater intensity exercise;
• Resort to weight lifting and cardio exercises to work certain areas of the body;
• Eat less saturated fats and change your snacking habits from sweets or high-fat snacks to fruit and vegetables;
• Keep hydrated to counterbalance loss of water from exercise;
• Include some “cheat days” for special occasions;
• Be persistent in following your plan.

References

Hodgdon JA. Body Composition In The Military Services: Standards And Methods; Institute of Medicine (US) Committee on Military Nutrition Research.

Jackson AS, Stanforth PR, Gagnon J, Rankinen T, Leon AS, Rao DC, Skinner JS, Bouchard C, Wilmore JH. The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study. Int J Obes Relat Metab Disord. 2002; 26(6):789-96.

Siri WE. Body composition from fluid spaces and density: Analysis of methods. In Brozek J, Henzchel A. Techniques for Measuring Body Composition. Washington: National Academy of Sciences. 1961; pp. 224–244.