The headline number
Raw, skinless, boneless chicken breast contains roughly 23-24g of protein per 100g, according to UK food composition data from McCance & Widdowson. Cook the same piece and you get around 28-31g per 100g cooked weight. Both figures describe identical protein content; the difference is simply that cooking drives off water, so each gram of cooked meat carries more protein by weight.
If you want one number to settle the question: a typical plain chicken breast cooked without skin delivers close to 30g of protein per 100g eaten.
The cooked-vs-raw catch
Most fresh chicken packs in supermarkets print their nutrition information per 100g of raw, uncooked weight. That is the standard for fresh meat under UK labelling rules. So the 23g per 100g figure on a Tesco or Sainsbury's label is describing the raw product, not what ends up on your plate.
Cooking removes roughly 20-25% of the weight as water evaporates. A 160g raw breast becomes roughly 120-130g on the plate. Because the protein itself doesn't cook away, that same amount of protein is now concentrated into fewer grams. The result is that 100g of cooked chicken breast contains more protein per gram than the raw label suggests.
| Per 100g raw (label figure) | ~23g protein |
| Per 100g cooked (what you eat) | ~30g protein |
| Weight loss during cooking | ~20-25% |
This matters for logging. If you weigh your chicken after cooking and then look up the raw-weight figure, you will underestimate the protein in your meal by a meaningful margin. The most accurate approach is either to weigh raw before cooking, or to specifically look up a cooked-weight entry.
What a real pack delivers
A fresh chicken breast from Tesco, Sainsbury's, Asda or Morrisons typically weighs 150-180g raw per piece. That is the standard range for the large single fillets most packs sell. Smaller lines, budget own-brand packs, or bone-in thigh-adjacent cuts can come in lighter.
Apply the cooking weight loss and a typical piece lands at around 115-135g cooked. At roughly 30g of protein per 100g cooked, that single breast delivers somewhere in the region of 33-40g of protein by the time it reaches your plate.
| Raw weight per breast (typical fresh fillet) | 150-180g |
| Cooked weight (after ~20-25% loss) | 115-135g |
| Protein in the cooked piece | ~33-40g |
Aldi (Roosters, Specially Selected) and Lidl (Birchwood, Deluxe) sell chicken breast at similar protein density per 100g to the major four. The protein difference between supermarket own-brand and premium lines is rarely meaningful; the bigger variables are fat content and whether the chicken has been basted or marinated.
Watch out for basted, marinated and breaded lines
Plain, skinless, boneless chicken breast is consistently high-protein and low-fat. The moment added water, oil, seasoning, brine, or a breadcrumb coating enters the picture, the numbers shift.
Basted and marinated lines often contain added water to tenderise the meat. Some pre-marinated Tesco, Asda or M&S lines declare 18-21g of protein per 100g rather than the 23-24g you get from plain. The protein is diluted by the extra mass of water and marinade. Breaded chicken fillets drop further still because a portion of the weight is now flour, breadcrumb and oil.
The label is the only reliable answer here. Look at the per 100g protein figure on the back panel rather than the front-of-pack claim. If it reads below 20g per 100g, there is likely water or coating involved.
What else is in there
Plain chicken breast is a lean protein source. A cooked 130g portion contains roughly 1-2g of fat, virtually no carbohydrate, and around 160-170kcal. The fat content rises meaningfully only when skin is left on or when the chicken is cooked in oil.
Beyond protein, chicken breast is a reasonable source of selenium, a trace mineral involved in thyroid function and antioxidant processes. It also provides good amounts of vitamin B6 (involved in protein metabolism) and niacin (B3), which contributes to normal energy metabolism. These won't make a huge dent in the day's target from a single portion, but they are a useful contribution.
Logging it without weighing every time
Weighing every chicken breast before cooking is accurate but not everyone's habit. A reasonable working estimate is to log a standard breast as 160g raw or 125g cooked, which gives you a sensible middle-of-the-road portion. The database in the app carries both raw and cooked chicken breast entries from major supermarkets, so you can pick whichever matches how you measured.
Logging "100g cooked chicken breast" returns the cooked-weight protein figure directly, with no adjustment needed. Logging a "1 chicken breast" portion in the app uses a 150g raw equivalent by default. For Pro subscribers, the 27-nutrient breakdown shows how the breast contributes to the day's selenium, B6 and niacin alongside protein.
A short, honest note
Protein targets vary considerably depending on your health situation, activity level and what a doctor or registered dietitian may have advised. This page describes what is in the food; it is not a recommendation of how much you should eat.