BoltzTraP is a code for calculating band-structure dependent quantities. It uses a smoothed Fourier interpolation of the bands to compute semi-classic transport coefficients. The method is based on an analytical representation of the bands, allowing for the calculation of derivatives necessary for transport distributions. The code has been tested against earlier calculations, showing excellent agreement with experimental values. It is implemented in Fortran90 and works on any system with a F90 compiler. The program uses the LaPack and Blas libraries and is designed to handle complex band structures, including those influenced by spin-orbit coupling. The code is easily portable and does not require large wavefunction files. It has been applied to various materials, including intermetallic compounds, high Tc superconductors, and thermoelectrics. The method is particularly effective for calculating transport coefficients, including the Hall coefficient, which depends on the second derivative of the bands. The code has been tested on Bi2Te3 and CoSb3, showing good agreement with experimental results. The method is also efficient for calculating higher-order derivatives needed for magneto-resistance. The code is interfaced with the WIEN2k code but can be adapted to other band-structure codes. The program outputs results in SI units and is suitable for a wide range of materials and conditions.BoltzTraP is a code for calculating band-structure dependent quantities. It uses a smoothed Fourier interpolation of the bands to compute semi-classic transport coefficients. The method is based on an analytical representation of the bands, allowing for the calculation of derivatives necessary for transport distributions. The code has been tested against earlier calculations, showing excellent agreement with experimental values. It is implemented in Fortran90 and works on any system with a F90 compiler. The program uses the LaPack and Blas libraries and is designed to handle complex band structures, including those influenced by spin-orbit coupling. The code is easily portable and does not require large wavefunction files. It has been applied to various materials, including intermetallic compounds, high Tc superconductors, and thermoelectrics. The method is particularly effective for calculating transport coefficients, including the Hall coefficient, which depends on the second derivative of the bands. The code has been tested on Bi2Te3 and CoSb3, showing good agreement with experimental results. The method is also efficient for calculating higher-order derivatives needed for magneto-resistance. The code is interfaced with the WIEN2k code but can be adapted to other band-structure codes. The program outputs results in SI units and is suitable for a wide range of materials and conditions.