Kingsoft Spreadsheet is the best free spreadsheet program for a couple of reasons - its beautiful, intuitive interface is super simple to use, and it supports a huge number of features.
It can work with the same file types as nearly every version of Microsoft Excel, like the XLSX, XLS, and CSV formats. Not only can you open those common file types but you can also save back to them, which is something not every free spreadsheet program allows.
This free spreadsheet software also supports over 100 formulas for working with data and has many more great abilities you'd expect to find in a spreadsheet program.
Two things I don't like is that there isn't an automatic spell check feature and you must download the entire Kingsoft Office suite even if you only want to install just the spreadsheet portion but not the word processor or presentation software.
OpenOffice Calc has many of the same features as Kingsoft Spreadsheets, including support for common file formats. However, it isn't nearly as easy to use.
With that being said, it has its own unique advantages, such as support for creating macros and an automatic spell check feature.
Also, OpenOffice Calc allows different tool sets to be detached from the main program window to provide more space for working while still providing access to tons of useful features.
The Extension Manager lets you add features to OpenOffice Calc that aren't included in the default program, which is another way you can customize the program to your liking.
Gnumeric is quite an advanced spreadsheet program. There are numerous tools you won't find in some of the other software from this list.
Though there are advanced, unique features like auto saving workbooks, it also has all the regular, common ones you'd expect to find in a spreadsheet program.
MS Excel 2003 and 2007 formats are supported and data can be imported from a text file and then filtered in Gnumeric.
Something else I like is that there's a very detailed online manual that you can use if you need help with any of the tools or options.
Like all of these spreadsheet programs, Spread32 supports hundreds of functions and all the regular formatting tools, but the program interface still manages to be super easy to use and provide a clean working space.
Files can be saved back to your computer in a number of formats like XLS, XLT, PXT, CSV, and BMP.
Spread32 is completely portable, which means you don't have to install it to use it and it can run from portable media like a flash drive. It takes up much less space than any of the other programs in this list, at just under a few megabytes.
Accel Spreadsheet doesn't look nearly as nice as the other programs from this list but it's still a working spreadsheet program that can perform many of the same functions.
Your files are able to be saved to formats like XLS and CSV but also to some Accel-specific ones like VTS and ATP.
A portable version of the Accel Spreadsheets software is available too.
Free Spreadsheet Programs
Five of the Best Microsoft Excel Alternatives
There are quite a few free spreadsheet programs out there that will give you the capabilities of Microsoft Excel without the expensive price tag. In fact, there's an awesome chance that you might even like one of these free programs better.
These free spreadsheet programs have all the spreadsheet functions you'd expect as well as some excellent features such as Excel file compatibility, clean interfaces, automatic spell check, macro creation, and auto-saving.