NuCraft (nucraft.hepforge.org) is an open-source Python project that calculates neutrino oscillation probabilities for neutrinos from cosmic-ray interactions in the atmosphere for their propagation through Earth. The solution is obtained by numerically solving the Schrödinger equation. The code supports arbitrary numbers of neutrino flavors including additional sterile neutrinos, CP violation, arbitrary mass hierarchies, matter effects with a configurable continuous Earth model, and takes into account the production height distribution of neutrinos in the Earth’s atmosphere. Program title: nuCraft Catalogue identifier: AEXK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEXK_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Revised BSD License No. of lines in distributed program, including test data, etc.: 3017 No. of bytes in distributed program, including test data, etc.: 467122 Distribution format: tar.gz Programming language: Python. Computer: IA32/x86-64 compatible. Operating system: All that are supported by SciPy, e.g., Linux, Windows, OS X. RAM: 134217728 bytes Classification: 1.1, 11.1, 11.6. External routines: NumPy (1.5.1 or newer), SciPy (0.8.0 or newer) Nature of problem: Calculation of oscillation probabilities of neutrinos that originate in cosmic-ray interactions in the Earth’s atmosphere and propagate through the Earth, for realistic Earth and atmospheric models and multiple flavors (optionally including sterile neutrinos and CP violation). Solution method: Direct solution of the Schrödinger equation for n flavors including matter effects, with sampling of the atmosphere. Restrictions: Energy loss and absorption of neutrinos inside the Earth is not modeled; they have to be handled independently. Unusual features: Completely configurable oscillation parameters (including optional sterile flavors), configurable and realistic Earth model including atmosphere. Running time: Roughly 100 neutrinos per second and CPU core (depends on energy and oscillation parameters).