let's say you bought two rolls of a product P (Tissue or Paper ....) (the unit of measure UoM when purchasing this product is a Roll or Unit ).

Known that, each roll is 2 meters large and 100 meters long.

Now you want to sell it with a another unit (like Meter), this is your UoS.

What you have to do, is to convert the original UoM to the new UoS before the sale.

1 Roll = 1 Unit = 100 meters, 100 is your Coefficient " Unit of Measure -> UOS Coefficient "

Now you can choose the unit meter as your UoS with a coefficient = 100, and begin selling this product in meter.

Another example is, when you purchase a Pallet of a Product B (In your Purchase invoice you get a purchase line like: Description = Product B ---- Quantity = 1 Pallet ---- Unit Price = 1000 € ---- Total Price = ......).

Known that each Palette contains 10 Boxes and each box contains 6 unit of this Product.

Now you have 60 unit of the product B to sell.

Your UoM to Uos coefficielt is 60.

Just fill the UoS and the Coefficient in your Product Form and begin selling this Product.

UoM to UoS or UoS to UoM, the UoS = UoM * Coefficient or UoM = UoS / coefficient

The long Answer

There are three parameters, which you can use:

The UoM, it's the unit of measure you specified when creating the product.

The UoS, it's the unit of sale (if any), you use for selling the product.

The UoP, it's the unit of purchase ( if any), used when purchasing the product.

Generally, UoM, UoS and UoP use the same unit of measure. But it happen that it uses different units, for the following reasons:

• Your Supplier(s) use another unit

• Your Customer(s) use a different unit

• You use different units, before and after manufacturing (if you are a manufacturer)

• You can also use different units, because of the packaging unit, and so on ...

In OpenERP those three units defaults to the unit "Unit" (also known as PCE) unless otherwise explicitly specified (e.g meter: m, Litre : L, Square meter : m², .....).

The default UoM "Unit": means 1 piece, or 1 item, or quantity = 1, of the related product. It's a generic unit of measure. It is used as UoM for products which not need to have a specific unit of measure in trading operations (e.g when selling, Hard Drive, egg, umbrella,...., we don't have to specify a unit of measure from The International System of Units).

What we should remember is:

That all those units are there as a mean of counting (quantification), and the important thing is the "Conversion Coefficient", when moving from one unit to another.

Let's take an example:

I've purchased 10 barrels of Wine, each barrel contain 500 liters.

My purchase order is labeled as follows:

• Product: Super Wine V7.0

• Quantity: 10

• Unit: Barrel

• Unit Price: 500 €

• Taxes: 0 %

• Total price: 5000 €

Now, i want to sell this product to my customers at 620 € the Barrel.

My first customer, needs 2 Liters (just enough for one night!).

I will sell to my customer 0.004 Barrel: 2 Liters = (1 barrel / 500) * 2 = 0.004 Barrel, keeping the same Unit of Measure (Barrel).

UoS = UoM * Coefficient

UoM = UoS / coefficient

Then i will use 500 as my Unit of Measure -> UOS Coeff

I have to fill this Coeff into the Unit of Measure -> UOS Coeff in the sales Tab of the product Form.

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And now you can see the result on runbot:

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The new unit - Category

https://www.dropbox.com/s/k3o7lrw8wbhwrek/New%20Unit-%20Categ.png?dl=0

Product sale price & UoM

https://www.dropbox.com/s/iswyowq64qh9a3q/Product%20%20Price%20UoM.png?dl=0

Product UoS & Coeff.

https://www.dropbox.com/s/v6n6f5skn7zodjo/Product%20UoS%20Coeff.png?dl=0

The Purchase Order

https://www.dropbox.com/s/jnrkozcxi8n95tv/Purchase%20order.png?dl=0

The Sale Order

https://www.dropbox.com/s/ms051mhz0rgbjda/Sale%20Order.png?dl=0

Where is the difference when using or not the UoS ?

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https://www.dropbox.com/s/ioi357n16xxwcuf/The%20Difference.png?dl=0