Compared with ALL older versions of software especially both Linux Office tells you what to do instead of performing what you ask for step by step. I often cannot find the way to repair what I did where in Windows this goes fine or is easy to correct. Beside that Open Office is very slow compared with Libre Office and Microsoft is still the fastest.
Zamzar - Free conversion online of many type of documents (images, text, video, audio...
Microsoft Office Excel - Microsoft Office Excel is a commercial spreadsheet application.
Online Convert - Convert files like images, video, documents, audio and more to other formats with this free and fast online converter.
Google Sheets - Synchronizing, online-based word processor, part of Google Drive.
Convertio - File Conversion in the Cloud
LibreOffice - Calc - LibreOffice Calc is the spreadsheet program you've always needed. A fork of OpenOffice.