The PTB Thermal Neutron Calibration Facility consists of sixteen 241Am-Be neutron sources mounted in a high-purity graphite block with dimensions of 150 cm x 150 cm x 180 cm at depths of between 115 cm and 135 cm from the front surface. The reference position for calibrations is 30 cm from the front surface of the graphite moderator device and 75 cm above the floor. Fluence values and dose equivalent quantities were determined by means of measurements and calculations for neutrons and (in some cases) for photons as well. The field is highly thermalized: 98.4 % in terms of fluence, and 86 % in terms of dose equivalent rate. The thermal neutron fluence rate at the reference position is (68.3 ± 1.9) cm-2s-1. The reference field is well-suited for the calibration of radiation protection devices. Zusammenfassung