A cap for a container with a hinged lid comprising a first part and a second part snap-engaged with each other on assembly, wherein: - the first part comprises a cylindrical base body which provides a first lower cylindrical portion having a larger diameter and a second upper cylindrical portion with a smaller diameter, coaxial with respect to each other, wherein said first lower cylindrical portion having a larger diameter is internally threaded in, so that it can be positioned on a screw neck of a mouthpiece of a container and said second upper cylindrical portion with a smaller diameter forms the pouring part of the cap, - the second part comprises a covering lid which provides an annular portion below and a lid portion above and a hinge arrangement consisting of a strip is interposed between said annular portion and said lid portion, - wherein the strip comprises weakened foldable end areas (53,54), connected to said annular portion and to said lid portion respectively, and a folding invitation line, centrally arranged longitudinally in the strip which divides the strip into two and defines two portions (39b,39c) between which a central recess is arranged, folding invitation lines also being provided (42,43,56 and 57) between said two portions (39b,39c) and said annular portion so that said lid portion can be moved between a closed position above said first part and a completely open overturned position alongside said first part, characterized in that said strip is arranged in a window opening, which is formed in the side surface of the lid portion and which is open towards the annular portion, and folding invitation lines (46, 47, 58 and 59) are also arranged between said two portions (39b, 39c) and an end edge of said opening in said lid portion. - the first part comprises a cylindrical base body which provides a first lower cylindrical portion having a larger diameter and a second upper cylindrical portion with a smaller diameter, coaxial with respect to each other, wherein said first lower cylindrical portion having a larger diameter is internally threaded in, so that it can be positioned on a screw neck of a mouthpiece of a container and said second upper cylindrical portion with a smaller diameter forms the pouring part of the cap, - the second part comprises a covering lid which provides an annular portion below and a lid portion above and a hinge arrangement consisting of a strip is interposed between said annular portion and said lid portion, - wherein the strip comprises weakened foldable end areas (53,54), connected to said annular portion and to said lid portion respectively, and a folding invitation line, centrally arranged longitudinally in the strip which divides the strip into two and defines two portions (39b,39c) between which a central recess is arranged, folding invitation lines also being provided (42,43,56 and 57) between said two portions (39b,39c) and said annular portion so that said lid portion can be moved between a closed position above said first part and a completely open overturned position alongside said first part, said strip is arranged in a window opening, which is formed in the side surface of the lid portion and which is open towards the annular portion, and folding invitation lines (46, 47, 58 and 59) are also arranged between said two portions (39b, 39c) and an end edge of said opening in said lid portion.