Food label portion calculator
Put the nutrition panel into the amount you plan to eat. A simple calculation, with no food diary, account or tracking.
Use the numbers on your packet
Calculate grams of a nutrient, kcal or kJ for a weighed portion. Nothing is sent or saved.
Arithmetic only. This does not recommend a portion, assess a food or set a dietary target. Use grams throughout; do not mix grams and millilitres.
How to use it
Choose the direction, enter one value from the nutrition panel and select its unit. Then enter the portion weight in grams. The default example turns 6g fibre per 100g into 1.8g fibre in 30g.
For the reverse direction, enter the value for the serving and that serving's weight. For example, 1.8g fibre in a 30g serving becomes 6g per 100g. This lets you compare two packets that suggest different serving sizes.
The NHS food labels guide explains the two columns. Our worked packet comparison shows why a smaller serving can make a number look smaller without changing the food.
What the result means
This tool scales the numbers you provide. It does not know which food you are eating, whether its label is correct or whether the panel describes food as sold or as prepared. Use the matching weight and preparation basis. It does not convert between grams and millilitres.
The result is rounded to at most three decimal places. That makes the arithmetic readable, not more precise than the original label. Entries stay in this browser page and are neither saved nor transmitted.
The formula, without the tool
Value per 100g × portion grams ÷ 100 = value per portion.
Value per portion × 100 ÷ portion grams = value per 100g.
Try high protein vs source of protein next. That claim uses a share of energy, a separate calculation from scaling a portion.