Ca3Ru2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), two equivalent O(1), and three equivalent O(4) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Ru(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing RuO6 octahedra. The corner-sharing octahedral tilt angles range from 27-30°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), and two equivalent Ru(1) atoms. In the second O site, O(2) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Ru(1) atoms to form distorted OCa3Ru2 trigonal bipyramids that share corners with four equivalent O(3)Ca2Ru2 tetrahedra, corners with two equivalent O(2)Ca3Ru2 trigonal bipyramids,  an edgeedge with one O(3)Ca2Ru2 tetrahedra, and edges with three equivalent O(2)Ca3Ru2 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ca(2) and two equivalent Ru(1) atoms to form distorted OCa2Ru2 tetrahedra that share corners with two equivalent O(3)Ca2Ru2 tetrahedra, corners with eight equivalent O(2)Ca3Ru2 trigonal bipyramids, and edges with two equivalent O(2)Ca3Ru2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to three equivalent Ca(1) and one Ru(1) atom.
Ca3Ru2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), two equivalent O(1), and three equivalent O(4) atoms. The Ca(1)-O(2) bond length is 2.48 Å. There is one shorter (2.30 Å) and one longer (2.54 Å) Ca(1)-O(1) bond length. There are a spread of Ca(1)-O(4) bond distances ranging from 2.28-2.39 Å. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Both Ca(2)-O(1) bond lengths are 2.68 Å. There is one shorter (2.35 Å) and one longer (2.40 Å) Ca(2)-O(3) bond length. There are two shorter (2.35 Å) and two longer (2.57 Å) Ca(2)-O(2) bond lengths. Ru(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing RuO6 octahedra. The corner-sharing octahedral tilt angles range from 27-30°. The Ru(1)-O(3) bond length is 1.98 Å. The Ru(1)-O(4) bond length is 1.99 Å. There is one shorter (1.98 Å) and one longer (1.99 Å) Ru(1)-O(1) bond length. Both Ru(1)-O(2) bond lengths are 2.01 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), and two equivalent Ru(1) atoms. In the second O site, O(2) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Ru(1) atoms to form distorted OCa3Ru2 trigonal bipyramids that share corners with four equivalent O(3)Ca2Ru2 tetrahedra, corners with two equivalent O(2)Ca3Ru2 trigonal bipyramids,  an edgeedge with one O(3)Ca2Ru2 tetrahedra, and edges with three equivalent O(2)Ca3Ru2 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ca(2) and two equivalent Ru(1) atoms to form distorted OCa2Ru2 tetrahedra that share corners with two equivalent O(3)Ca2Ru2 tetrahedra, corners with eight equivalent O(2)Ca3Ru2 trigonal bipyramids, and edges with two equivalent O(2)Ca3Ru2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to three equivalent Ca(1) and one Ru(1) atom.