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# ⚖️ Track items sold by weight from your POS

If you sell an item by weight (for example, prawns by the kilo), you can configure haddock to track the real consumption and inventory, no matter which POS you use.

## How it works

When the POS sends a sale, it tells haddock **how many units** of an item were sold. To work with weight, we use a small trick: we create a recipe costing where **1 unit = 1 kg** of the product. Then haddock automatically converts the units the POS reports into the right amount of product consumed.

* If the POS sends **1 unit** sold → haddock discounts **1 kg** from inventory.
* If the POS sends **0.25 units** sold → haddock discounts **0.25 kg**.
* If the POS sends **2.5 units** sold → haddock discounts **2.5 kg**.

This works the same way for any POS integrated with haddock.

## Step-by-step

For example, if you sell prawns both **by portion** and **by the kilo**:

1. In your **POS**, make sure you have a **dedicated item for the by-weight sale**, separate from the by-portion item. For example, "Prawns by weight" and "Prawns portion" should be two different articles in the POS.
2. In **haddock**, create a recipe costing called something like *"Prawns by weight"*.
3. Add a **single ingredient** to that costing: the product *Prawns*, with a quantity of **1 kg**.
4. [Link that costing](https://support.haddock.app/en/article/create-recipe-costings-from-your-pos-items-1tewt3s/) to the *"Prawns by weight"* POS item.
5. Repeat with a separate costing for the by-portion item, with its real portion size (for example, 0.2 kg).

That's it. From then on, every by-weight sale your POS sends will be reflected as the right number of kilos in your theoretical inventory and sales reports.

## If your POS is Revo

In Revo, turn on **"Precio por peso"** (price by weight) on the item. Revo then sends the weighed kilos with each sale, and haddock uses them as the quantity sold. Without this option, each sale arrives as 1 unit.

The weight arrives in the same unit the item is priced in. If the price is per kilo, create the costing for 1 kg. If it is per 100 g, create it for 100 g.

## Important limitation

The POS item linked to the by-weight costing must be used **only** for sales by weight. If the same POS article is used for both portions and weight, haddock cannot know whether each sale was a portion or a number of kilos, and the consumption will be wrong.

If your POS allows it, create one article for the by-weight variant and another for the by-portion variant, each linked to its own costing in haddock.

## Related articles

* [🥘 Create recipe costings from your POS items](https://support.haddock.app/en/article/create-recipe-costings-from-your-pos-items-1tewt3s/)
* [Add ingredients to a recipe costing](https://support.haddock.app/en/article/add-ingredients-to-a-recipe-costing-1jdk78/)
* [Convert ingredients to a base unit (kg, l or units) for recipe costings](https://support.haddock.app/en/article/convert-ingredients-to-a-base-unit-kg-l-or-units-for-recipe-costings-l3admi/)