Net carbs

Net carbs subtract the carbohydrate that is not absorbed as glucose — fibre, and in most versions the sugar alcohols — from a food's total carbohydrate. The concept comes from low-carbohydrate and ketogenic dieting, where the practical question is how much a food raises blood glucose rather than how much carbohydrate it technically contains.

It matters because the two numbers can differ substantially in high-fibre foods, and because keeping to a low carbohydrate intake is much easier when vegetables and nuts are counted by their absorbed carbohydrate.

In practice the term is not a regulated definition, and food manufacturers have used it liberally on packaging — sugar alcohols vary in how much they are actually absorbed, so a 'low net carb' bar is not always what the label implies. Outside a ketogenic context, total carbohydrate is the simpler and safer number to work with.