Skip to content
LiveCriée
FR

Buyer's guides

Fish and seafood size grades:standards, price lists and prices

Size grades explained: minimum sizes, EU categories and price list grades for sea bass, Dover sole, turbot, monkfish, king scallop, oysters, lobster.

Updated 8 min readLiveCriée editorial team

Contents
  1. What are the three size grade grids?
  2. The correspondence table, species by species
  3. How to read oyster size grades?
  4. What effect does the size grade have on price and yield?
  5. What are the pitfalls of size grades on a price list?
  6. Frequently asked questions

The size grade (calibre) is the size class of a fish, crustacean or shellfish, expressed as weight per piece ("1/2 kg"), as number of pieces per kilo ("20/30") or as a measurement ("11 cm"). On a price list (mercuriale), it is often the factor that makes the price vary most, after the species.

Three grids coexist, and they do not overlap: the minimum size set by fisheries regulations, the size categories of the European marketing standards, and the commercial size grades that each fish merchant (mareyeur) writes in their own way.

What are the three size grade grids?

GridWho sets itWhat it is forWhere you come across it
Minimum size (minimum conservation reference size)European Union, Regulation 2019/1241; sometimes stricter national rulesBelow it, the product cannot be sold for direct human consumptionRarely written; it sets the smallest possible size grade
Size categories 1 to 5European Union, Regulation (EC) 2406/96 (marketing standards)Classifying lots at first sale; 1 is always the largestAt the fish auction, on sale slips and lot labels
Commercial size gradesEach fish merchant, according to trade practiceDescribing what they sell to their customersOn price lists: "1/2 kg", "500/800", "20/30"

The minimum size protects the resource; the category organises the sale at the fish auction; the commercial size grade speaks to the buyer. A fish merchant buys in categories, sorts again in their workshop, then sells in commercial size grades.

The correspondence table, species by species

SpeciesEU minimum sizeCategories of Regulation 2406/96Examples of use on price listsWhat you need to know
Sea bass42 cm in the English Channel, North Sea and Celtic Seas; 36 cm in the Bay of Biscay, raised to 40 cm by France for its professional fishermen; 25 cm in the MediterraneanNoneWild: 0.8/1 kg, 1/2 kg, 2/3 kg, +3 kg. Farmed: 300/400 g, 400/600 gA 42 cm sea bass weighs about 770 g, a 36 cm sea bass about 490 g (Ifremer): a "300/400" sea bass caught in the Atlantic or the Channel would be under the legal size, so it generally comes from farming
Dover sole24 cm (Atlantic and Channel)1: 0.5 kg and over; 2: 0.33 to 0.5; 3: 0.25 to 0.33 (the text says 0.35, which overlaps category 2); 4: 0.20 to 0.25; 5: 0.12 to 0.20"Sole 1" to "sole 5", or 200/300 g, 300/400 g, 400/500 g, +500 gA 24 cm Dover sole weighs about 115 to 125 g (Ifremer), roughly the lower limit of category 5
TurbotNo European size in the Atlantic and the Channel; 30 cm for French vesselsNone1/2 kg, 2/3 kg, 3/4 kg, +4 kg; farmed often 1/2 kgLarge fish are cut into thick portions (pavés) with a better yield
Monkfish (anglerfish)NoneWhole gutted: 1: 8 kg and over; 2: 4 to 8; 3: 2 to 4; 4: 1 to 2; 5: 0.5 to 1. Headless: 1: 4 kg and over; 2: 2 to 4; 3: 1 to 2; 4: 0.5 to 1; 5: 0.2 to 0.5Tail 0.5/1 kg, 1/2 kg, 2/4 kg, +4 kgIn France, monkfish is mostly sold as tails: the size grade applies to the tail, not to the whole fish
John DoryNoneNone0.5/1 kg, 1/2 kg, +2 kgLarge head: about 35% fillets for a 1 kg fish (Seafish)
King scallop100 mm; 110 mm in the eastern Channel (division 7d); for French vessels, 10.2 cm or more on several bedsSingle size: 10 cm and overWhole shell by the kilo; scallop meat by number per kilo (10/20, 20/30, 30/40)As with langoustine, the smaller the number per kilo, the larger the scallop meat
Pacific oysterNone (farmed)NoneNo. 0 to 5 (see below); "fine" or "spéciale"The number gives the weight, the category gives the flesh content
Flat oysterNone (farmed)NoneIts own numbers, with repeated "0"s for the largestIts own scale, not to be confused with that of Pacific oysters
LangoustineTotal length 85 mm in the North Sea and North Western waters, 70 mm further south; 9 cm for French vessels in the Bay of BiscayWhole: 1: 20 pieces per kilo and fewer; 2: 21 to 30; 3: 31 to 40; 4: more than 40. Tails: 1: 60 and fewer; 2: 61 to 120; 3: 121 to 180; 4: more than 18010/15, 15/20, 20/30, 30/40, 40/60; live or deadThe smaller the number, the larger the langoustine
European lobster87 mm carapace length; 9 cm for French vessels since 1 August 2026None300/400 g, 400/600 g, 600/800 g, +800 gThe size is measured on the carapace, not on the total length

Sources: Regulation (EU) 2019/1241, Annexes V to VII and IX (European minimum sizes); French order of 28 January 2013 (French sizes for professional fishing); Regulation (EC) No 2406/96, Annex II (size categories, lower limit included, upper limit excluded); Ifremer, length-weight relationships (weight of fish at minimum size). The "examples of use" column gives size grades noted by the editorial team on price lists: they are not standards, each fish merchant writes their own.

How to read oyster size grades?

Pacific oysters are graded by weight per piece, with a number: the smaller it is, the larger the oyster.

Pacific oysterWeight per oyster
No. 0more than 150 g
No. 1121 to 150 g
No. 286 to 120 g
No. 366 to 85 g
No. 446 to 65 g
No. 530 to 45 g

Grid from the 2015 interprofessional agreement on the naming and classification of Pacific oysters, used by the French Ministry of the Sea in its exam papers.

Flat oysters have their own scale of numbers, with repeated "0"s for the largest. No official weight grid has been found: ask your supplier for the weight per piece.

The number says nothing about the flesh. For that, Pacific oysters carry a category according to their fill index, the share of drained flesh in the total weight: fine from 6.5 to 10.5 (excluded), spéciale from 10.5. A spéciale No. 3 is fleshier than a fine No. 3, for the same shell weight.

What effect does the size grade have on price and yield?

The price per kilo is not proportional to the size grade. Large fish are often more expensive per kilo, because they are rarer and more in demand in restaurants. But they yield more: according to Seafish, a 750 g turbot gives about 50% of its weight in fillets, and a 3 to 4 kg turbot 60% in thick portions. The food cost guide shows with an illustrative sea bass example that a size grade 26% more expensive per kilo can cost only 10% more on the plate.

For products sold by the piece, the size grade changes the cost of the portion. Two calculation examples, at equal price per kilo:

ProductSize grade ASize grade BWhat it changes
Dozen Pacific oystersNo. 3, about 75 g each: 0.9 kgNo. 2, about 103 g each: 1.24 kgAt equal price per kilo, the dozen No. 2 costs about 35% more
Plate of 6 langoustines30/40, 25 to 33 g each: 150 to 200 g20/30, 33 to 50 g each: 200 to 300 gAt equal price per kilo, the plate in 20/30 costs about 40% more

Average weights calculated by the editorial team at the middle of the size grade ranges.

What are the pitfalls of size grades on a price list?

  • Open-ended ranges. "+1 kg" can cover a fish of 1 kg as well as one of 4 kg. Ask for the actual range of the lot.
  • Overlapping size grades. "1/2 kg" from one fish merchant and "1.5/2.5 kg" from another do not describe the same lot: comparing them requires bringing both to the same basis, as the price list guide explains.
  • Whole, gutted or headless. The size grade of a monkfish tail has nothing to do with that of a whole monkfish.
  • Wild or farmed. For sea bass, sea bream and turbot, small regular size grades often betray farming. The production method must appear on the documents.
  • The size grade of the season. At the start of the king scallop season or at the end of the langoustine season, the available size grades change: the seasonality calendar helps anticipate this.

Frequently asked questions

What does "20/30" mean for a langoustine?

Between 20 and 30 pieces in a kilo, that is langoustines of 33 to 50 g. The smaller the number, the larger the langoustine: a 10/15 is much larger than a 30/40.

What is the largest Pacific oyster size grade?

No. 0, above 150 g per oyster. No. 5 is the smallest, between 30 and 45 g. For flat oysters, the scale goes from 000 (the largest) to 6.

What does "calibre 1" mean on a fish auction slip?

The largest size category within the meaning of European Regulation 2406/96. For Dover sole, it is 500 g and over; for headless monkfish, 4 kg and over.

What is the minimum size of a sea bass?

42 cm in the English Channel, the North Sea and the Celtic Seas, under European Regulation 2019/1241; 36 cm in the Bay of Biscay under this regulation, raised to 40 cm by France for its professional fishermen; 25 cm in the Mediterranean. A 42 cm sea bass weighs about 770 g (Ifremer).

Large or small size grade: which is more profitable?

It depends on the cut. The large size grade often costs more per kilo but yields more usable flesh. The calculation is done portion by portion, with your own yield measured in the kitchen.

Sources

Read next