Shrimp count sizes: the 2.2 factor that skews your quotes

A shrimp count size is a number of pieces per unit of weight: 16/20 means 16 to 20 shrimp per pound (453.6 g), or 35 to 44 per kilo. The same figure on a quote can be read per pound or per kilo, and the gap between those two readings is a factor of 2.2. I'm dwelling on this because a misreading on a container costs you in the sizes that turn up, not in a few cents of discount.

This article starts with the definition, works through the conversion figures, then shows how count size distorts a real order and which lines to write into your spec to protect yourself.

What is a shrimp count size, and what unit is it measured in?

A shrimp count size is the range of pieces that make up one unit of weight: 31/40 means 31 to 40 shrimp per pound. The lower the number, the bigger the shrimp. The FAO's Codex Alimentarius, in its standard for quick frozen shrimps or prawns, defines size designation as a number of pieces relative to a weight.

What catches buyers out is the unit, because the trade doesn't use just one.

Why do two scales, per pound and per kilo, exist side by side?

The per-pound scale comes from the US trade, and it's the one Vietnamese export plants use to quote vannamei: 16/20, 21/25, 26/30, 31/40. The per-kilo scale is the one used by fishmongers and many French wholesalers, with bands such as 10/15, 20/30 or 40/60, as you can see on the sizing page of the fishmonger pierrotcoquillages.com.

The two notations look alike on paper, which is where the risk lies. According to a-la-fine-maree.fr, a 16/20 holds 16 to 20 shrimp in 450 g, or 35 to 44 per kilo. Conversely, a 40/60 on the kilo scale is only 18 to 27 pieces per pound, so these are bigger shrimp than a 31/40 on the pound scale.

A count size without a unit isn't a specification, it's a guessing game.

Some retail labels make things even harder by showing a single number. In his video, the fishmonger Christophe (Chezmonpoissonnier channel) explains that a "cal 50" means 50 to 70 shrimp per kilo, so 5 to 7 pieces per 100 g. For 300 g of size 100 (80 to 100 per kilo), he counts 24 to 30 shrimp. That shorthand works at the counter. In a container contract, I don't accept it.

Conversion table: how many shrimp per kilo for each count size?

To go from a per-pound count to pieces per kilo, simply divide by 0.4536. A 16/20 gives 35 to 44 pieces per kilo, a 41/50 gives 90 to 110, and a 61/70 gives 134 to 154. According to restaurant-laccostage-ouistreham.fr, the full range runs from 8-12 all the way to 150-200 for very small shrimp.

How do you read this table without getting it wrong?

The middle column converts the range into pieces per kilo. The last column answers the question a chef asks: how much do 8 shrimp weigh, the usual portion for a starter? Average weight per piece is calculated from the midpoint of each range.

My own Search Console dashboard confirms there's interest in this topic: over the 30 days to 9 September 2026, our size chart from U10 to 80/100 page logged 410 impressions and 4 clicks. The volume is modest, but the site's average position (7.7) shows the topic is winnable. Our readers are mostly looking for a conversion, and that's why this table exists.

Raw, cooked, head-on or headless: what basis is the count based on?

A count size only holds for one specific shrimp form. A HOSO vannamei (head and shell on), a HLSO (headless) and a PDTO (peeled, tail on) of the same nominal count have neither the same weight nor the same value. If the quote doesn't state the form, the buyer is comparing different products.

Why does the same count change weight depending on form and cooking?

The head accounts for roughly a third of the weight of a whole vannamei. So a HOSO 31/40 shrimp is noticeably smaller, once the head is off, than a HLSO 31/40. According to a-la-fine-maree.fr, cooked shrimp weigh about 20 to 25% less than raw shrimp of the same count, and the shell makes up 30 to 40% of the total weight. A kilo of raw shrimp therefore yields 750 to 800 g of cooked.

Comparing two prices per kilo without comparing form and cooking basis is like comparing the whole fruit with its stone.

How does glazing distort the count?

Glaze is the thin layer of ice that protects frozen shrimp. If the count is done on the gross glazed weight, each shrimp looks lighter than it really is. Take a lot invoiced as 31/40 with 20% glaze, counted on gross weight: about 35 pieces per 453.6 g gross, which contains only 363 g of meat. Each shrimp then weighs 10 g and the real net count is around 44 pieces per pound, in other words a 41/50 sold under a 31/40 label.

The mechanism is covered in detail in our article on glazing rates. For count size, the rule is simple: the count is based on net drained weight, never on gross weight.

What count size changes in a container order

In an import order, each count size is a separate price line: the bigger the shrimp, the higher the price per kilo. This is nothing new; back in 2018, recettesjecuisine.com was already noting for the retail trade that price rises in step with size. In B2B the gap plays out by the tonne, and slipping one full count size across a lot is enough to wipe out a margin.

Why does a bigger count weigh so heavily on portion cost?

Back to the table. Eight 31/40 shrimp weigh 102 g, eight 16/20 shrimp weigh 202 g: the weight served doubles while the number of pieces on the plate stays the same. For a restaurant, portion cost therefore tracks the weight of each piece as much as the price per kilo. We rework this calculation with glaze and yield in our article on shrimp portion cost in foodservice.

This arithmetic matters to whoever signs for a container. A single restaurant doesn't buy a 20' FCL: it reads, compares and passes the spec on to its importer or buying group. For an importer, a seafood wholesaler or a processor, the real question is what each count size costs, plant by plant, per net kilo.

We source FOB Ho Chi Minh City, with an MOQ of 1×20' FCL (mixed references possible), usually landing at Le Havre or Antwerp. To price your grid, request an FOB quote by count size and format, with a reply within 48 hours.

What to write into your purchase spec on count size

A purchase spec protects you if it pins down the unit, the counting basis, the tolerance and the inspection method. Each line below addresses a flaw covered above: ambiguous unit, unstated form, glaze counted in the weight. The tolerance values are starting points I suggest, open to negotiation with the plant.

Which lines should you demand from the supplier?

• Unit: "Count expressed in pieces per pound (453.6 g), e.g. 31/40." No per-kilo scale appears anywhere in the contract.
• Form and basis: "Raw Penaeus vannamei shrimp, HLSO, counted before any cooking."
• Net weight: "Count based on net drained weight, after deglazing, with maximum glaze declared (e.g. 10%)."
• Tolerance: "At least 90% of pieces in the sample within the stated range, no pieces outside the two adjacent counts."
• Method: "Sample per lot, deglazed in cold water, weighed, counted, result converted to net pound."
• Documents: "Count stated per carton on the packing list and the plant certificate."

The inspection method on arrival is detailed in our guide Shrimp count size: how to prove what you paid for, and the contract wording for the range in 16/20 doesn't mean 16 to 20 per kilo.

Verdict: specify count per pound, on raw shrimp, at net weight

Write the count in pieces per pound, on raw shrimp at net drained weight, and reject any quote that doesn't state its unit and basis. That's the answer to the question raised at the start: the 2.2 factor only skews a quote when the unit isn't written down.

Should a contract use pounds or kilos?

Adopt: pounds, because that's how Vietnamese plants quote, and converting to pieces per kilo takes one division when the end customer asks for it. Test: a 90% tolerance on a first container, with a joint count at Le Havre or Antwerp, before tightening it on later orders. Avoid: any count expressed as a single number, any range with no mention of glaze, and any price comparison that mixes HOSO, HLSO and PDTO.