Given a value of the Fermi-Dirac integral ∫0∞tjdtet−η+1, this routine returns the value of the parameter η for a given j with a relative error less than 10−13. The inversion is provided for η∈[−30,100] and for the following set of j values, {−1/2,1/2,3/2,5/2,1,2}. For η∈[−30,−2], an iterative method involving the McDougall and Stoner series is used. For the rest of the region of interest, a rational fit is employed. Program summaryProgram title: InvFDCPC Library link to program files:https://doi.org/10.17632/rc8x92mx8n.1Licensing provisions: GPLv3Programming language: Octave-4.2.2Nature of problem: Quite often in solid-state physics applications, given a value of the Fermi-Dirac integral defined by ∫0∞tjdtet−η+1, one needs the value of the parameter η, for a given j where j∈{−1/2,1/2,3/2,5/2,1,2}. The η values considered lie in the range [−30,100], a typical region of interest for solidstate physics applications.Solution method: For η∈[−30,−2], an iterative scheme based on the McDougall-Stoner series is utilized. For the remaining interval [−2,100], a rational fitting is provided. The relative error of the η evaluation is less than 10−13.Additional comments including restrictions and unusual features: Provides inversion for both integer and half-integer Fermi-Dirac integrals. The relative accuracy is close to double precision.