I am trying to plot an FFT in LTspice using a .four command and the spice error log directly without using the FFT on LTspice (right click + view + FFT once the simulation is finished).

How is it possible to plot the data of the .four command at the end of the simulation from the spice error log?

Here is an example of the spice error log:

enter image description here

I cannot right click on the spice error log and plot FFT measured by the .four command.

  • 1
    \$\begingroup\$ It can't plot it before the sim is ran so it has to be afterwards. \$\endgroup\$
    – Andy aka
    Commented Feb 14, 2022 at 12:57
  • \$\begingroup\$ If all else fails, extract that part of the file and import it into a spreadsheet. (But the data shown is only the harmonics, not the full FFT) \$\endgroup\$
    – user16324
    Commented Feb 14, 2022 at 13:47

1 Answer 1


You can't plot the result of the .FOUR, that's meant to be a report in the error log, only. But you can plot the FFT of a waveform by making the waveform viewer window active > RClick > View > FFT. For the best results, be sure to include an integer number of periods for the waveform.


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