Is there any international standard for stock evaluation? if yes can you state and explain it?

IFRS2 Share-based Payment requires an entity to recognise share-based payment transactions (such as granted shares, share options, or share appreciation rights) in its financial statements, including transactions with employees or other parties to be settled in cash, other assets, or equity instruments of the entity. Specific requirements are included for equity-settled and cash-settled share-based payment transactions, as well as those where the entity or supplier has a choice of cash or equity instruments.

IFRS2 was originally issued in February2004 and first applied to annual periods beginning on or after1 January2005.

These inventories should be measured at the lower of cost and net realisable value. Net realisable value is the estimated selling price in the ordinary course of business less the estimated costs of completion and the estimated costs necessary to make the sale. The basic principles are the same as SSAP9. 

Yes there is an International Accounting Standard IAS2- Inventory, states that Inventory(stock) is valued at lower of cost or net realisable value.

Cost means the purchase price plus any directly attributable expenditure bringing the inventory to its present location and condition.

Net realisable value NRV is the sale price less any selling cost.