Calorie Needs Calculator Formula

Understand the math behind the calorie needs calculator. Each variable explained with a worked example.

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Formulas Used

Maintenance Calories

maintenance = bmr * activity_factor

Weight Loss (500 deficit)

weight_loss = bmr * activity_factor - 500

Weight Gain (500 surplus)

weight_gain = bmr * activity_factor + 500

Basal Metabolic Rate

bmr_display = bmr

Variables

VariableDescriptionDefault
weight_lbsWeight(lbs)170
height_inches_totalHeight (total inches)(inches)70
ageAge(years)30
activity_factorActivity Level1.55
weight_kgDerived value= weight_lbs * 0.453592calculated
height_cmDerived value= height_inches_total * 2.54calculated
bmrDerived value= 10 * weight_kg + 6.25 * height_cm - 5 * age + 5calculated

How It Works

How Daily Calories Are Calculated

This calculator uses the Mifflin-St Jeor equation, considered the most accurate formula for estimating calorie needs.

Formula (Male)

BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5

TDEE = BMR x Activity Factor

A 500 calorie deficit results in approximately 1 lb of fat loss per week.

Worked Example

A 30-year-old male, 170 lbs, 5'10", moderately active.

weight_lbs = 170height_inches_total = 70age = 30activity_factor = 1.55
  1. 01Weight in kg: 170 x 0.4536 = 77.1 kg
  2. 02Height in cm: 70 x 2.54 = 177.8 cm
  3. 03BMR = 10(77.1) + 6.25(177.8) - 5(30) + 5 = 1,733
  4. 04TDEE = 1,733 x 1.55 = 2,686 calories/day

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