The effects of Ca2+ on bio-membranes are of interest because of their role in several biological processes, including facilitating the membrane fusion process. In a recent study, we have investigated a cushioned [1] DPPC bilayer in water and in different concentration CaCl2 solutions via fluid exchange. We used a polymer (PAA) cushion deposited on a single crystal silicon substrate. Using a 22 keV X-ray beam at the beamline of Sector 8 at the Advanced Photon Source, we obtained high resolution reflectivity from the bilayer and cushion through water, and were also able to study the grazing incidence x-ray diffuse scattering. The effect of Ca2+ on the bilayer structure has been obtained from the reflectivity analysis, which shows the Ca2+ ions binding to the headgroups of outer leaflet of the DPPC bilayer. The diffuse scattering is used to obtain the physical properties such as the surface tension, bending modulus, etc. Combining both, we present a complete picture of how Ca2+ affects a DPPC bilayer in water at room temperature as a function of Ca2+ concentration.