Bale forming apparatus for forming a round-cylindrical bale from loose material, wherein the bale forming apparatus comprises - a bale forming means (7, 21.1, 21.2) comprising an endless pressing means, - a tensioning arrangement for the pressing means, - a bale pushing element, and - a casing (5, 6) comprising a moveable casing part, wherein the tensioning arrangement comprises - a tensioning actuator, - a first pivotally mounted tensioning member (13, 14, 16.1, 16.2) comprising at least one first guiding element (16.1, 16.2), and - a second pivotally mounted tensioning member (17, 18) comprising at least one second guiding element, wherein the bale pushing element is mechanically connected with the first tensioning member (13, 14, 16.1, 16.2), wherein the moveable casing part is moveable between - a bale forming position and - a bale ejecting position, wherein the casing (5, 6) with the moveable casing part being in the bale forming position surrounds a bale forming chamber, wherein the bale forming means (7, 21.1, 21.2) is arranged to form the cylindrical bale in the bale forming chamber surrounded by the casing (5, 6), wherein the casing (5, 6) with the moveable casing part being in the bale ejecting position provides an aperture for ejecting the formed bale out of the bale forming chamber, wherein the pressing means is guided - around the first guiding element (16.1, 16.2) of the first tensioning member (13, 14, 16.1, 16.2) and - around the second guiding element of the second tensioning member (17, 18), and wherein the tensioning actuator tends to pivot the second tensioning member (17, 18) away from the first tensioning member (13, 14, 16.1, 16.2), thereby applying a tensioning force onto the pressing means, wherein the pressing means being guided around both tensioning members (13, 14, 16.1, 16.2, 17, 18) tends to pivot the second tensioning member (17, 18) against the force of the tensioning actuator towards the first tensioning member (13, 14, 16.1, 16.2), wherein the bale forming apparatus is arranged such that the tensioning actuator tends to pivot the second tensioning member (17, 18) away from the first tensioning member (13, 14, 16.1, 16.2) in both positions of the moveable casing part, wherein the bale forming apparatus is arranged such that the pressing means surpasses the force of the tensioning actuator as long as the moveable casing part is in the bale forming position, and the tensioning actuator surpasses the force of the pressing means if the moveable casing part is in the bale ejecting position. wherein the tensioning arrangement is arranged such that pivoting the second tensioning member (17, 18) away from the first tensioning member (13, 14, 16.1, 16.2) pivots the first tensioning member (13, 14, 16.1, 16.2) towards the bale in the bale forming chamber and causes the connected bale pushing element - to contact the bale and - to push the bale towards the moveable casing part wherein the bale forming apparatus comprises a distance sensor, wherein the distance sensor is arranged to measure a value indicative of the distance between the two guiding elements (16.1, 16.2, 18). - a bale forming means (7, 21.1, 21.2) comprising an endless pressing means, - a tensioning arrangement for the pressing means, - a bale pushing element, and - a casing (5, 6) comprising a moveable casing part, - a tensioning actuator, - a first pivotally mounted tensioning member (13, 14, 16.1, 16.2) comprising at least one first guiding element (16.1, 16.2), and - a second pivotally mounted tensioning member (17, 18) comprising at least one second guiding element, - a bale forming position and - a bale ejecting position, - around the first guiding element (16.1, 16.2) of the first tensioning member (13, 14, 16.1, 16.2) and - around the second guiding element of the second tensioning member (17, 18), and - to contact the bale and - to push the bale towards the moveable casing part