PoshanSensePer 100 g is not your portion. Your chai deserves better maths.
A worked example for converting calories per 100 grams into your actual portion, without mistaking a serving for the whole packet.
Worked examples explain the calculation, not a personal nutrition target.
A nutrition label is trying to be helpful. Then it introduces “per 100 g”, “per serving” and “servings per pack” in the same tiny rectangle. Suddenly your snack has become a maths assignment. The good news: you only need one consistent basis and the amount you actually ate. The chai can stay warm.
Start with the unit, not the biggest number
Label values apply to a stated amount of food. The FDA’s label explainer explains serving sizes and multiplying values when more than one serving is eaten. That source describes US labels; the worked calculations here do not depend on US daily-value recommendations.
On your own packet, find whether the calories are shown per 100 grams, per serving, per pack or per 100 millilitres. Choose one column. Then measure your portion using the same type of unit. Grams describe mass and millilitres describe volume; do not silently swap them.
One snack. Three honest numbers.
The one-line calculation
Portion calories = label calories × amount eaten ÷ label amount. For our invented 400-kcal-per-100-g snack, a 30 g portion is 120 kcal. A 60 g portion is 240 kcal. The per-100-g number stays the same; the amount eaten changes.
If the label instead says 120 kcal per 30 g serving, the same calculation gives 240 kcal for 60 g: 120 × 60 ÷ 30. You have reached the same answer by a different column. Do not add the two columns together. They are alternative descriptions of the food, not two separate ingredients.
A packet is not automatically a serving
Imagine a fictional 90 g packet with the values above. The whole packet would contain 360 kcal by this example calculation. If you ate a third, you ate 30 g, or 120 kcal. If you shared it, record your amount rather than the quantity printed on the front. “One packet” can mean different sizes even for products with similar names.
When you cannot weigh a portion, use the clearest estimate available and say what it represents. “Half of a 90 g pack” is easier to interpret later than “some snacks”. Precision is helpful when it is practical; pretending an uncertain portion is exact does not make it exact.
The cup-of-chai complication
For homemade chai, a packet label may describe only one ingredient. Milk and sugar need their own amounts; water is not another serving of milk. A premix label might describe the powder before preparation, while another product gives values for the prepared drink. Read the preparation notes before entering a cup into your journal.
Our example is about keeping units consistent, not estimating your particular recipe. If you routinely make the same pot, write down its ingredients and the number of comparable cups it yields. Use that as a working description and adjust when the recipe changes. A tiny cup and a large mug should not share a mysterious universal “one chai” value.
Check once, then make future logging easier
Before saving a food entry, ask three questions: Which amount does this value describe? How much did I eat? Are the units compatible? That little check often matters more than whether your result displays one decimal place or three.
Use the portion calculator for the arithmetic. It runs in your browser and does not send its inputs to us. You can also read our label guide for another example. Neither tool decides how much you should eat; it helps describe the amount you chose.
A final serving of perspective
Labels and portion estimates have limits. Treat the result as a useful record, not a moral score for the meal. Consistency makes your journal easier to understand over time. Perfect arithmetic cannot rescue a guessed unit, and an honest estimate is better than a beautifully formatted wrong answer.
Sources & further reading
Cover art is AI-generated conceptual illustration; it does not depict actual study meals. Diagrams are original PoshanSense graphics. Paper figures and publisher images are not reproduced. Examples and practical interpretations are identified in the text.
Published 5 October 2026 · Sources checked 5 October 2026. Suggest a correction.