How to Calculate Energy Intake for a 13-Year-Old Girl

The Estimated Energy Requirement (EER) is the amount of energy, or calories, a person must consume daily to maintain her current body weight. A person's EER is dependent on variables such as gender, age, weight, height and how much physical activity the person engages in. If a girl is involved in a sport that requires maintaining a particular body weight or just wants to watch her figure, calculate her energy intake by performing a few simple mathematical calculations.

Things You'll Need

• Tape measure
• Calculator
• Pencil
• Paper
• Bathroom scale

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Instructions

• 1

  Measure the girl's height. Enter the number into the calculator and multiply it by 0.305 to convert it from feet and inches to meters. (e.g. if the girl is 5 feet tall, multiply 5 by 0.305 to get 1.525 meters). Write this information down for later use.

• 2

  Check the girl's weight on a scale. Enter the number into the calculator and multiply it by 0.454 to convert the number from pounds to kilograms (e.g. if the girl weights 110 pounds, multiply 110 by 0.454 to get 49.94 kilograms), Write this information down for later use.

• 3

  Determine the girl's physical-activity coefficient (PA). If she has a sedentary lifestyle, with little to no physical activity, her PA would be 1. If her physical activity is low active, meaning she walks between 1.5 and 3 miles a day, her PA is 1.16. If she is physically active, meaning she walks more than 3 miles a day, her PA is 1.31. Write this number down.

• 4

  Enter the numbers you gathered into a mathematical formula to determine the girl's EER. The formula for girls age 9 to 18 is as follows: EER= 135.3 - ( 30.8 x AGE) + PA x ( 10 x WT + 934 x HT) + 25. Input the age (13), height (HT), weight (WT) and physical activity level (PA) into the equation and enter the equation in a calculator. For example, for a 13 year-old girl who is 1.525 meters tall and weighs 49.94 kilograms with a PA of 1.31, the equation could look like EER= 135.3 -- (30.8 x 13) + 1.31 x (10 x 49.94 + 934 x 1.525) + 25. The EER of the girl would be 2280.0125.