We have found one software suitable in our database for this conversion.
Using the TI CellSheet Converter utility provided by Texas Instruments, it should be possible to transfer simple spreadsheets saved in Microsoft Excel format (.xls, .xlsx) to your TI device, including TI-NSpire, which is what xls to tns conversion achieves.
For other graphics calculators, the utility will convert it to other format suitable on that specific device.
XLS
Files with xls extension are best known as spreadsheets from Microsoft Excel. A spreadsheet is basically a grid of cells sorted in rows and columns. Each cell can contain text, numeric or formula data. Excel XLS spreadsheets can be opened in most other similar programs, such as OpenOffice.org Calc.
TNS
Files with tns extension can be mainly found as documents for TI-Nspire range of graphic calculators produced by Texas Instruments