Convert GRAMS / Galactic .spc files to CSV

The .spc format comes from Galactic's GRAMS software, and many programs still write it: FTIR, UV-Vis, NIR and Raman software from PerkinElmer, Thermo Nicolet, HORIBA, Ocean Optics, Andor, Kaiser, WITec and others, and Bruker OPUS as an export. This page writes the spectra from any of these .spc variants as CSV, without GRAMS.

How to convert SPC to CSV

1. Upload one .spc, a selection of them, or a zipped folder.
2. Choose the number format: decimal points, or decimal commas for European Excel settings.
3. Download the CSV. Its header carries the axis names and units stored in the file, such as Wavelength (nm) or Raman shift (cm-1).

Single and multi-spectrum files

An .spc can hold one spectrum or many, and the CSV follows the structure:

• Single spectrum: an x column and a y column.
• Multifile with a shared x axis (a kinetic run, a temperature series): one column per spectrum, headed with its z value from the file, for example Time (min) = 0.5.
• XYXY files, where every spectrum has its own x values (GC-MS scans, for instance): the spectra keep their own x columns instead of being forced onto one axis.
• Maps and long series on a shared axis switch to rows once they pass 100 spectra: each row is one spectrum, labelled with its z value, which keeps the table within spreadsheet limits. More options lets you choose the layout yourself.

Versions and variants

Both the current format and the older LabCalc-era layout are read, with integer (16- and 32-bit) or floating-point data, evenly or unevenly spaced x, and the optional log block. Twenty-six real files from different instruments were checked against two independent open-source SPC readers and against text exports.

Where those readers disagree, this converter follows the format specification. In some multi-spectrum files, for example, each spectrum has its own scaling exponent, which can be negative; readers that ignore this report some spectra two to four times too large.

Shimadzu .spc files

Shimadzu's UVProbe software uses the .spc extension for a different, unrelated format. The converter tells the two apart by their content and reads both, so you don't need to know which kind you have. Shimadzu UVProbe .spc to CSV has the details.

Other outputs

You also get an Excel workbook with a chart and metadata, and a JCAMP-DX file. All supported formats are listed on the Spectrum File Converter page.

More about what this tool reads and writes: Spectrum File Converter (OPUS, OMNIC, SPC, WDF, SP, JWS).