The time it takes to convert an OST (Offline Storage Table) file to a PST (Personal Storage Table) file can vary depending on several factors. Here are some factors that can influence the conversion time if you are using the third-party OST to PST Converter software:

• Size of the OST file: Larger OST files generally take more time to convert compared to smaller ones. The size of the file is determined by the amount of data it contains, such as emails, attachments, contacts, calendars, etc.
• Hardware and software specifications: The speed and performance of your computer and the efficiency of the OST to PST conversion tool you are using can affect the overall conversion time.
• Network and system resources: If you're performing the conversion over a network or your system is running multiple processes simultaneously, it can slow down the conversion process.
• Complexity of the OST file: If the OST file is damaged, corrupted, or contains a complex folder structure, it may take longer to convert as the conversion tool needs to handle these complexities.

Given these variables, it's difficult to provide an exact time frame for the conversion process. However, in general, the conversion process can take anywhere from a few minutes to several hours, depending on the factors mentioned above.