The invention concerns a calender provided with an extended nip for calendering of a paper or board web. The calender comprises at least one calendering nip (N), which is formed between a heatable hard roll (1) and a calendering belt (10) which has been formed as an endless loop and which is loaded against the heatable hard roll (1) by means of a backup roll (3) or a press shoe (24). The paper or board web (W) to be calendered is arranged to run through said calendering nip (N). According to the invention, in respect of at least a part of its thickness, the calendering belt (10) is made of a material of compressible volume. According to a second embodiment of the invention, the necessary resilience in the nip (N) is provided by means of a separate support belt, which runs underneath the calendering belt in relation to the web (W).