There are numerous ways to keep track of inventory quantities for different business applications. Four important quantities are:

Quantity on Hand – This is the total quantity of a product that you have in your inventory storage. This does not include products that have been picked for a Sales Order. This type of quantity is the most commonly shown when working with your inventory, such as in the Current Stock screen.

Quantity Reserved – This is the quantity of the product that has been ordered by a customer, but has not yet been picked or shipped out. This represents the quantity of the product that would be required to fulfill all existing Sales Orders.

Quantity on Order – This is the total quantity of this product that have been ordered from vendors but not yet received. This represents the extra amount of the product that is expected to be received in the future.

Quantity Available – This is the quantity of the product that is on hand and has not yet been promised to a customer, so is available for sale. This quantity is obtained by subtracting the Quantity Reserved from the Quantity on Hand. (i.e. Quantity Available = Quantity on Hand – Quantity Reserved).