A blank for forming a disposable cup, the blank comprising a cardboard sheet designed to be formed into a body of a cup, preferably in a form of a truncated cone, the blank comprising - a first edge in a form of a first arc for forming the bottom edge of the cup, - a folding line for forming the rim of the cup, wherein the folding line for forming the rim of the cup contains a first folding line formed by a plurality, such as 4-10, of interconnected arc-shaped folding lines each arcing to the opposite direction than the first arc, and wherein a foldable wing extends form each arc-shaped folding line, wherein tips of the wings are configured to be folded towards the center of the formed cup to lock onto each other to form a cover over the opening of the cup, each of the foldable wings extending form each arc-shaped folding line are partly interconnected at the folding line end forming a continuous area between the first folding line and a second edge at the opposite end of the blank than the first edge, the continuous area being in a form of an arc which is substantially parallel to the first folding line, wherein each of the foldable wings contain at the continuous area a first folding surface formed by a second folding line and a third folding line, the second and the third folding lines extending from the first end and the second end of each arc-shaped folding lines and forming an angle (α), such as an angle (α) of 40-50°, wherein the tip of a wing points away from the first folding line, and wherein the second folding line and the third folding line are formed to be able to fold to form the cover, preferably wherein a second folding line of a wing and a third folding line of an adjacent wing meet each other at an end of an arc-shaped folding line, characterised in that the tips of the wings extend from the second edge. - a first edge in a form of a first arc for forming the bottom edge of the cup, - a folding line for forming the rim of the cup, wherein the folding line for forming the rim of the cup contains a first folding line formed by a plurality, such as 4-10, of interconnected arc-shaped folding lines each arcing to the opposite direction than the first arc, and wherein a foldable wing extends form each arc-shaped folding line, wherein tips of the wings are configured to be folded towards the center of the formed cup to lock onto each other to form a cover over the opening of the cup, each of the foldable wings extending form each arc-shaped folding line are partly interconnected at the folding line end forming a continuous area between the first folding line and a second edge at the opposite end of the blank than the first edge, the continuous area being in a form of an arc which is substantially parallel to the first folding line, wherein each of the foldable wings contain at the continuous area a first folding surface formed by a second folding line and a third folding line, the second and the third folding lines extending from the first end and the second end of each arc-shaped folding lines and forming an angle (α), such as an angle (α) of 40-50°, wherein the tip of a wing points away from the first folding line, and wherein the second folding line and the third folding line are formed to be able to fold to form the cover, preferably wherein a second folding line of a wing and a third folding line of an adjacent wing meet each other at an end of an arc-shaped folding line, characterised in that the tips of the wings extend from the second edge.