Calender (1) for calendering a paper or board web (2), having at least one nip (3), which is formed between a heatable roll (4) and a mating element (5), a device (6) for producing a predetermined pressure in the nip (3), and a web treatment device (7) arranged upstream of the nip (3) and having two contact surfaces (9, 10) forming a treatment nip (8), one of which is a circulating contact surface (9) which is formed by a belt (14) circulating on guide rolls (11, 12, 13), the other contact surface (10) is formed by the circulating surface of the heatable roll (4), and the treatment nip (8) extends along an angle (15) of the wrap of the heatable roll (4), wherein, in order to increase the thermal efficiency of the transfer of heat, the circulating belt (14) uses a resilient surface to press the paper or board web (2) onto the heatable roll (4), and the guide rolls (11, 12, 13) control sectional forces of the circulating belt (14) in the treatment nip (8).