Device for estimating humidity in construction materials. Device (1) for estimating humidity and temperature in construction materials, comprising a body of plastic (2) transparent or translucent prismatic with a first base (3) open, a thermo-hygrometer (5) with a screen (8) oriented towards the second base (4), a fan (6) facing the first base (3), an on/off device (7) of the fan (6) and, sealing means of the plastic body (2) in the edge of first base (3). Method for estimating humidity in building materials, by means of this device (1) with the phases formed by coupling the device (1) by its first base (3) open on the construction material, fan ignition (6), wait for 5-30 minutes, obtaining the relative humidity of the air, and estimating the humidity of the material. (Machine-translation by Google Translate, not legally binding)