The odds of getting a knife in CS:GO vary depending on the source, but they are generally very low. Here are the odds cited by various sources:

• 0.21% chance, or approximately 1 knife every 500 boxes
• 0.26% chance, or approximately 1 knife every 400 cases
• 0.3% chance, or approximately 1 knife every 333 cases

Its important to note that these are just estimates and the actual odds may vary. Additionally, opening cases in CS:GO can be a costly and risky endeavor, as the odds of getting a knife or other valuable item are low. Its generally recommended to trade your way up to a knife or purchase one from a skin exchange website like Tradeit or the Steam Market.