Safe, free and unlimited xls to xlsx converter?

[Mayhem]

I am in the situation that I need to convert a large number of xls sheets to xlsx to be compatible with my version of Excel. It is an institution license so I cannot convert manually due to the security restrictions imposed on the license by my institution.

I know there is a slew of online converters. These work PERFECTLY, except nearly all (if not all) require premium subscriptions for unlimited conversions. Does anyone know of a free and safe piece of software that performs this task automatically? I'd prefer if you have personal experience with it, as it's hard to know what can be trusted.

Thanks!

 

[pbuk]

I don't understand: xlsx is a newer format than xls so any version of Excel that can read xlsx files can also read xls.

 

[pbuk]

I don't understand: xlsx is a newer format than xls so any version of Excel that can read xlsx files can also read xls.

Or do you mean that the institution's installation of Excel (presumably on a machine controlled by the institution on which you do not have administrator access) prevents you from opening .xls files?

In this case I think you will need to do the conversion on another machine. You can get a 1 month trial of Office 365 for free.

Alternatively fork out the c.USD10 for 500 conversions at e.g. CloudConvert.

 

[berkeman]

It is an institution license so I cannot convert manually due to the security restrictions imposed on the license by my institution.

It sounds to me like you need to talk to your IT department about your question. If they have restrictions on the conversion for security reasons, they likely will not want you using some random tool to do the conversions.