All companies are tasked with buying products for internal use or for selling if they are manufacturing companies or a distributor. Either way, there needs to be some sort of measurement associated with the products that are being purchased. The company can buy stock in centimeters, but the vendor sells them in meters, so at the time of reception of the goods they have to be converted to these measurements, Fortunately, Odoo has a function called UOM that automatically converts the measure from meters to centimeters and vice versa at the time of ordering. 

The function has to be activated from settings in the Inventory module, under the products section. There are various categories you can choose from eg.g unit, weight, length/ distance, working time, or volume. Select the appropriate category in relation to the product you are purchasing. It also allows you to do a round of precision for example of an amount between one and two units. 

Odoo will take the unit, ratio, and the rounding precision into account when ordering the new products so that it makes conversions for the new product being ordered by the organization. 

When checking on the product at hand it will show you the UoM that you sell with and not the UoM that you bought with from the vendor, e.g if you were buying a rope for a roll and you bought 100 meters, it will show you 100,000 cm. No need to do any conversions at all on your end. 

The organization in turn tends to keep track of the precise amount that has been purchased and not lose any units from their end. UoM is a way of saving costs.