How to read a UK food nutrition label

To read a UK nutrition label, look at two columns: "per 100g" and "per serving". The per 100g column lets you compare products fairly and is what you scale to the amount you actually eat. Then read the rows in order: energy (shown as kJ and kcal, use the kcal), fat, of which saturates, carbohydrate, of which sugars, fibre, protein and salt. The reference intakes at the bottom (2,000 kcal for women, 2,500 kcal for men) are just a yardstick, not your personal target. Once you can read those, logging accurately is mostly weighing the food and doing a little arithmetic.

Here is how each part works.

Per 100g vs per serving

Every UK label must show the values per 100g (or per 100ml for drinks). Many also add a "per serving" column. They do different jobs.

• Per 100g is the honest comparison column. Two cereals sat side by side can look similar until you compare per 100g and one has twice the sugar. Use this column to compare products and to work out what you actually ate.
• Per serving is the manufacturer's chosen portion, and it is often smaller than what you pour or scoop. A "serving" of crisps might be 30g when the bag holds 150g.

The safe habit: weigh what you eat, then scale from the per 100g figures. If a snack is 480 kcal per 100g and you eat 40g, that is 480 x 0.4, so 192 kcal. Trusting the per-serving number without weighing is the most common way people undercount.

Energy: read the kcal, not the kJ

Energy is listed twice: kilojoules (kJ) first, then kilocalories (kcal). They measure the same thing in different units. In the UK we count calories in kcal, so that is the number you log. As a rough sense-check, 1 kcal is about 4.2 kJ, so a food showing 840 kJ is roughly 200 kcal.

The macro rows, in order

UK labels list nutrients in a set order, with two indented "of which" rows sitting under their parent:

Two points that trip people up. First, "of which sugars" is already counted inside the carbohydrate figure, so do not add them together. Second, in the UK the carbohydrate number already excludes fibre, so the carb figure you see is closer to what most trackers call "net carbs".

For logging, the three rows that carry calories are fat, carbohydrate and protein. Using the 4/4/9 rule (protein and carbs at 4 kcal per gram, fat at 9 kcal per gram) you can sense-check the energy figure. Say a portion has 5g fat, 20g carbs and 6g protein: that is 45 plus 80 plus 24, so about 149 kcal, which should land near the stated energy.

Traffic lights on the front

Many UK packs carry front-of-pack colour coding: red, amber or green for fat, saturates, sugars and salt, per serving. Red is not banned, it just means high, so keep an eye on how often that food shows up across your day. It is a quick glance, not a substitute for the back-of-pack figures you log from.

Reference intakes explained

At the bottom you will often see reference intakes, sometimes shown as a percentage. These are based on an average adult eating 2,000 kcal a day for women and 2,500 kcal a day for men. They are population averages set for labelling, not a goal picked for you.

Your own daily calorie target depends on your height, weight, age and how active you are, and it is usually different from 2,000 or 2,500. So treat the "%RI" on a label as a rough guide to how much a food contributes, and set your real target from your own numbers. Our BMR and TDEE guide walks through working that out.

Turning the label into an accurate log

Put it together and accurate logging is four steps:

1. Weigh the food on kitchen scales, in grams. Guessing portions is where most errors creep in.
2. Read the per 100g column for energy and the macros.
3. Scale to your weight. For 65g of something listed per 100g, multiply each figure by 0.65.
4. Log the fat, carbs and protein, and let the calories follow.

Fresh food without a label, like an apple or a chicken breast, works the same way once you have a trusted per 100g figure to scale from.

Let the app do the scaling

The scaling arithmetic is where a tracker earns its keep. Fettle (stayfettle.com) reads UK labels through barcode scanning, so you scan the pack, type the grams you ate, and it works out the calories and macros for you. It has UK foods built in, it is free, and there is no account to set up.

One honest note

This is general guidance on reading labels, not medical or dietary advice. If you have a health condition, a food allergy, are pregnant, or follow a specific eating plan for medical reasons, check with your GP or a registered dietitian before making changes.