A sheet packaging material for producing a sealed package containing a food product, said sheet packaging material comprising a first edge, a second edge parallel to the first edge, a third edge, a fourth edge parallel to third edge, the third and fourth edges (3, 4) joining the first and second edges (1, 2) such that the sheet packaging material has a rectangular shape, a first crease line and a second crease line that extend in parallel between the first and second edges (1, 2), a third crease line and a fourth crease line that extend in parallel between the first and second edges (1, 2) and intermediate the first and second crease lines (11, 12), a fifth crease line and a sixth crease line that extend between the first and second crease lines (11, 12), a seventh crease line and an eight crease line that extend between the first and second crease lines (11, 12) and intermediate the fifth and sixth crease lines (15, 16), the crease lines dividing the sheet packaging material into - a rectangular, central portion configured to form a top panel of the sealed package, - a first side portion and a second side portion that are adjacent the central portion and opposite each other, and configured to form a first side panel and a second side panel of the sealed package, - a third side portion and a fourth side portion that are adjacent the central portion and opposite each other, and configured to form a third side panel and a fourth side panel of the sealed package, and - two end portions (55a, 55b) that are adjacent two of the side portions (53, 54) and configured to be joined to each other to form a bottom panel of the sealed package, characterized in that the seventh and eight crease lines (17, 18) comprise a first pair of crease sections (17a, 18a) that define two opposite sides of the first side portion, wherein the first pair of crease sections (17a, 18a) are angled towards each other such that the first side portion has a trapezoidal shape, and the seventh and eight crease lines (17, 18) comprise a second pair of crease sections (17b, 18b) that define two opposite sides of the second side portion, wherein the second pair of crease sections (17b, 18b) are angled towards each other such that the second side portion has a trapezoidal shape. a first edge, a second edge parallel to the first edge, a third edge, a fourth edge parallel to third edge, the third and fourth edges (3, 4) joining the first and second edges (1, 2) such that the sheet packaging material has a rectangular shape, a first crease line and a second crease line that extend in parallel between the first and second edges (1, 2), a third crease line and a fourth crease line that extend in parallel between the first and second edges (1, 2) and intermediate the first and second crease lines (11, 12), a fifth crease line and a sixth crease line that extend between the first and second crease lines (11, 12), a seventh crease line and an eight crease line that extend between the first and second crease lines (11, 12) and intermediate the fifth and sixth crease lines (15, 16), the crease lines dividing the sheet packaging material into - a rectangular, central portion configured to form a top panel of the sealed package, - a first side portion and a second side portion that are adjacent the central portion and opposite each other, and configured to form a first side panel and a second side panel of the sealed package, - a third side portion and a fourth side portion that are adjacent the central portion and opposite each other, and configured to form a third side panel and a fourth side panel of the sealed package, and - two end portions (55a, 55b) that are adjacent two of the side portions (53, 54) and configured to be joined to each other to form a bottom panel of the sealed package, characterized in that - a rectangular, central portion configured to form a top panel of the sealed package, - a first side portion and a second side portion that are adjacent the central portion and opposite each other, and configured to form a first side panel and a second side panel of the sealed package, - a third side portion and a fourth side portion that are adjacent the central portion and opposite each other, and configured to form a third side panel and a fourth side panel of the sealed package, and - two end portions (55a, 55b) that are adjacent two of the side portions (53, 54) and configured to be joined to each other to form a bottom panel of the sealed package, characterized in that the seventh and eight crease lines (17, 18) comprise a first pair of crease sections (17a, 18a) that define two opposite sides of the first side portion, wherein the first pair of crease sections (17a, 18a) are angled towards each other such that the first side portion has a trapezoidal shape, and the seventh and eight crease lines (17, 18) comprise a second pair of crease sections (17b, 18b) that define two opposite sides of the second side portion, wherein the second pair of crease sections (17b, 18b) are angled towards each other such that the second side portion has a trapezoidal shape.