Serving Size Calculator Formula

Understand the math behind the serving size calculator. Each variable explained with a worked example.

Use the Serving Size Calculator

Formulas Used

Your Calories

your_calories = label_calories * ratio

Your Protein

your_protein = label_protein * ratio

Serving Ratio

serving_ratio = ratio

Variables

VariableDescriptionDefault
label_serving_gLabel Serving Size(g)30
your_serving_gYour Serving Size(g)55
label_caloriesCalories Per Label Serving(kcal)140
label_proteinProtein Per Label Serving(g)3
ratioDerived value= your_serving_g / label_serving_gcalculated

How It Works

How to Calculate Nutrients for Any Serving Size

Divide your actual serving by the label serving to get a ratio, then multiply each nutrient by that ratio.

Formula

Ratio = Your Serving / Label Serving

Your Nutrient = Label Nutrient x Ratio

Worked Example

Cereal label says 30g serving has 140 calories and 3g protein. You eat 55g.

label_serving_g = 30your_serving_g = 55label_calories = 140label_protein = 3
  1. 01Ratio = 55 / 30 = 1.83
  2. 02Your calories = 140 x 1.83 = 257 kcal
  3. 03Your protein = 3 x 1.83 = 5.5 g

Ready to run the numbers?

Open Serving Size Calculator