Conversion of units

How melba performs unit conversions to calculate the right quantities and costs

Published on 04/28/2021Sébastien Vassaux

How melba performs unit conversions to calculate the right quantities and costs

The unit system has been described in other articles in the same section.

So you know that a unit is associated with a quantity, a type, another unit and can be used in a given context: purchase, sale, production, storage.

Time and again, melba systems convert from one unit to another to bring you a relevant result.

Conversion of units of weight

This case is the simplest. Melba has a correspondence table of all the weight units in the international system.

To convert two units, melba determines from this table the factor that connects the two units and applies it to the conversion quantity.

Example: to convert 3 kg to g, quantity 3 is multiplied by the factor 1000 (since a 1kg = 1000g) and therefore 3kg = 3000g

Conversion involving a unit of volume

The units of volume can benefit from an additional parameter carried by the product, density.

When we convert a unit of weight into a unit of volume, we first convert the unit of weight in kg, then the kg in L with the consideration of density, then the L in the unit of volume given.

So, if we want to convert 500mL into g for a product of density 1.2, we have: 500mL = 500 * 0.1 L / mL * 1.2 kg / L * 1000 g / kg = 600g

Conversion involving a piece type unit

The pieces are units which come out of the international system and which can be chained.

Thus, we can have a batch of 10 packages of flour with a package of 1kg. If we introduce a case of 100 packs of 0.5kg each and we want to convert a case into a lot, we will do: 1 case = 100 packages / case * 0.5 kg / package * 1 kg / kg * 0.1 lot / package = 5

In the specific case of recipes and portions, it must be taken into account that melba automatically calculates the weight of recipes and portions according to the elements that are included in the recipes. The same logic will then be adopted for the conversion of the piece type units which are the recipe and the portion.

Conversion to account for weight loss when transforming a recipe

When transforming a recipe, its weight can:

  • increase: example of pasta cooked in water
  • decrease: example of the baked baquette

In these two cases, the weight of the final recipe will not be equal to the sum of the weights of the elements added to the recipe.

Thus, the elements added to the recipe have a net weight which participates in the gross weight of the recipe. This recipe can then possibly undergo a transformation and have a net weight different from its gross weight.

Example: if I compose a salad with pasta and I put a dough recipe in my salad, the weight of the salad will take into account the net weight of the pasta which is different from the gross weight of the pasta used.

If I compose the salad with 1kg of dough (we mean cooked pasta), then I will need less raw pasta to get these 1kg of cooked pasta.

So if the weight gain is 100% when cooking pasta and I want to make 2kg of salad with 1kg net of vegetables, I should use the following amount of raw dough: 

Q = [2 kg - 1 kg (of vegetables)] / (1 + 100%) = 0.5 kg of raw pasta.

Conversion to account for weight loss during the transformation of the article

Weight loss can also be done on the item before using it in the recipe.

So, if the vegetables from the previous recipe are peeled before use, they will lose weight, for example 10%.

To make 2kg of salad, I will therefore need:

  • 0.5 kg of raw pasta which cooked in water will give me 1 kg of cooked pasta
  • 1kg / (1 - 10%) = 1.11 kg of raw vegetables which, peeled, will give 1kg of net vegetables.

Order quantities are therefore affected by variations in the weight of the items.

Likewise the costs are affected. Costs are always associated with purchase quantities reduced to units that have a gross weight. So always calculate the gross usage amount of an item to determine its cost in revenue.

Example: if I order a 3kg crate of vegetables at a cost of 4 € / kg and I want to make my recipe of 2kg of salad, I will need 1.11kg gross of vegetables. The cost in the recipe will therefore be 1.11kg * 4 € / kg = 4.44 €. The quantity actually purchased will be rounded up to the packaging, ie 3kg for a total cost of 12kg.

In conclusion

Converting units is not easy to understand.
However, we will remember:

  • Melba has a correspondence table of all the weight units in the international system.
  • The weight of a recipe will take into account the net weight of the items.
  • The units of volume can benefit from an additional parameter carried by the product, density.
  • A recipe can undergo transformation and have a net weight different from its gross weight
  • Order quantities are therefore affected by variations in the weight of the items.