XLS to FTS Converter

Export XLS spreadsheets as FTS FITS images online

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Scientific Standard

FTS follows the FITS standard used in astronomy and research — convert your XLS data for use in scientific imaging pipelines.

Cloud-Powered

No local scientific software required. Our servers handle the XLS to FTS conversion while your device stays free.

Secure Processing

Uploaded XLS files are deleted immediately. FTS results are removed within 24 hours.

How to convert XLS to FTS

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose fts or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your fts file right afterwards

About formats

XLS is the binary spreadsheet format of Microsoft Excel, first introduced with Excel 1.0 for Macintosh in September 1985 and becoming the dominant spreadsheet format worldwide. The format stores workbooks as OLE2 compound document files using the Binary Interchange File Format (BIFF), organizing sheets, cells, formulas, formatting, charts, pivot tables, macros, and metadata across multiple internal streams. Each cell record encodes the cell's value (number, string, boolean, error, or formula), position, and formatting index, while shared string tables and style records reduce redundancy. The format evolved through BIFF versions (BIFF2 through BIFF8), with BIFF8 (Excel 97) establishing the structure used through Excel 2003. XLS supports up to 65,536 rows and 256 columns per sheet, a limit that drove the creation of XLSX. One advantage is universal spreadsheet compatibility — XLS files are recognized by every major spreadsheet application including LibreOffice Calc, Google Sheets, Apple Numbers, and dozens of programming libraries across all platforms. The format's mature feature set is another strength: XLS handles complex formulas, conditional formatting, data validation, named ranges, array formulas, external references, and VBA macros. Although XLSX replaced XLS as the default in Office 2007, the binary format persists in financial institutions, legacy reporting systems, and any environment where Excel 97-2003 compatibility is required.
Developer: Microsoft
Initial release: September 1985
FTS is a file extension for the Flexible Image Transport System (FITS), the standard data format used in astronomy since 1981 when it was defined by Don Wells, Eric Greisen, and R.H. Harten at the National Radio Astronomy Observatory, and subsequently endorsed by the International Astronomical Union in 1982. FITS was designed from the outset as a self-describing archival format: each file begins with one or more 2880-byte header blocks containing ASCII keyword-value pairs that describe the data's dimensions, coordinate system, observation parameters, and provenance, followed by data blocks in a variety of numeric types — 8/16/32/64-bit integers and 32/64-bit IEEE floating-point values. FITS supports multi-dimensional arrays (images, data cubes, hypercubes), binary tables for catalog data, and ASCII tables, with multiple Header/Data Units (HDUs) that can coexist in a single file. The format handles specialized astronomical data: spectral cubes, radio interferometry visibilities, multi-extension mosaic images from CCD arrays, and time-series photometry. One advantage is scientific rigor: FITS mandates that all metadata needed to interpret the data physically — coordinate transformations (WCS), photometric calibration, telescope and instrument parameters — travels with the file, eliminating the metadata-loss problem that plagues general-purpose image formats in scientific contexts. The format's longevity and institutional backing is another strength — virtually every observatory, space telescope (Hubble, James Webb, Chandra), and astronomical software package (DS9, IRAF, Astropy) uses FITS as its primary data format.
Developer: NASA / IAU
Initial release: 1981

Frequently Asked Questions

Why convert XLS to FTS?

FTS is a FITS-family format used in astronomy and science — converting from XLS creates images compatible with scientific analysis tools.

What opens FTS files?

SAOImage DS9, FITS Liberator, Aladin, and various astronomical software packages open FTS files for scientific image analysis.

Is FTS a standard format?

FTS follows the FITS (Flexible Image Transport System) standard, widely used in astronomy for storing images and tabular data.

Is it free to convert?

Yes — convertio.tools converts XLS to FTS at no cost. Premium plans provide batch conversion and extended features.

Does it work in my browser?

The entire conversion is browser-based. No scientific software installation needed — just upload and download.