Why Calorie Apps Give Different Numbers for the Same Food.

On 4 October 2026, we compared selected Tesco Chicken Club entries in YAZIO, Nutracheck, MyFitnessPal, MyNetDiary, Cronometer and NutraSafe with Tesco’s current product page. The app screens showed 504–508 kcal. Tesco listed 506 kcal per pack.

That is a small spread. The more useful differences were the portion information, the way carbohydrates were labelled and the ingredient detail available in NutraSafe. Here are the figures and the screens, so you can see what each observation supports.

We make NutraSafe. This is one product across six selected entries, searched by name on the founder’s phone and captured as screenshots. We did not scan the barcode in any app or photograph the physical pack. It is an observation, not an independent accuracy ranking.

*MyNetDiary’s “T. Carbs” includes fibre: 53g carbohydrate + 4g fibre = 57g total. MyFitnessPal’s 61.8g sits beside 5.6g of fibre on the same entry. UK label carbohydrate excludes fibre. Cronometer explicitly says “Net Carbs”; net-carb calculations can also subtract sugar alcohols. See the explanation below before comparing these columns. Portions remain unverified.

NutraSafe and MyNetDiary matched Tesco’s displayed energy value. Every selected entry was within 2 kcal of it, or less than 0.4%. That does not establish which app is most accurate across a weekly shop. Tesco’s website is a retailer reference, and recipes can change: the current pack is the next check.

MyNetDiary’s 57g “T. Carbs” uses the US-style total carbohydrate convention, which includes fibre. A UK pack’s “carbohydrate” figure excludes fibre. The two headings describe different totals, so comparing them directly can make an entry look further from the pack than it is.

In the MyNetDiary entry, the nutrient table shows 53g carbohydrate and 4g fibre. Together they make the macro summary’s 57g total. That explains the 4g difference between its two displays; it is a change of definition, not evidence of an arithmetic error.

There is still a separate product-record comparison to make: its fibre-excluded 53g is 3.5g below Tesco’s online 56.5g. One reading is that the entry began with Tesco’s 56.5g, which already leaves fibre out, and took the 4g off a second time. We have not established that; matching the current barcode, recipe and portion would be needed. The US convention does not account for all differences between the selected entries.

MyFitnessPal shows 61.8g carbs, 5.3g above Tesco’s UK figure. The same entry lists 5.6g of dietary fibre, and 61.8g less 5.6g is 56.2g, so it reads as carbohydrate with the fibre added in. It is a member-submitted entry, and we have not established how the figure was arrived at. Cronometer explicitly shows 56.5g Net Carbs. Nutracheck shows 56.5g carbs, NutraSafe 56.6g and YAZIO 56.7g. Keep each app’s label with the number when comparing them. Do not subtract fibre again from the carbohydrate figure on a UK label.

Portions need checking too. YAZIO shows 250g, Cronometer 249g and NutraSafe 249.2g. Nutracheck and MyFitnessPal show “pack” without a weight, and MyNetDiary says Weight: N/A. The screenshots alone cannot establish the cause of every numerical difference.

We checked the names and codes against the Food Standards Agency’s E-number list. The roles below follow Tesco’s ingredient declaration for this sandwich.

The app’s list has a seventh entry for yeast extract, an additional ingredient shown separately from those six E-number groups. “Seven things added” is therefore not a count of seven distinct E-number additives. E451 itself groups two named triphosphates in the recipe.

An E-number identifies an additive; the function tells you why it is used. The FSA’s explanation of food additives describes roles including preserving food, reducing oxidation and helping ingredients mix. Our E-number library gives you somewhere to read further.

These names do not tell us how much of each additive is in a pack. EFSA’s explanation of dietary exposure uses both concentration in food and the quantity eaten. This case checks the displayed ingredients and nutrition figures; it does not validate the app’s health classifications or measure anyone’s exposure.

A July 2026 study published in Nutrition and Health evaluated 17 nutrition apps available in Türkiye. It compared nutritional calculations from 13 apps against standardised three-day food records; ten overestimated energy intake. The researchers noted substantial variation and the limits of using standardised menus.

That is evidence that apps can disagree with a reference calculation. It does not establish which app currently scans UK supermarket products most reliably. These findings do not establish NutraSafe’s accuracy on current UK products. They should not become a claim that one app is always accurate or always inaccurate.