A prosthetic heart valve includes a radially expandable stent and a plurality of leaflets. Each leaflet includes a coaptation portion, an arcuate edge, and a belly. The coaptation portion is movable relative to respective coaptation portions of the other leaflets. The arcuate edge has a first end and a second end and is coupled to the stent. The belly extends from the arcuate edge to an axis defined by the first and second ends of the arcuate edge, wherein the ratio of the surface area of the belly to the outer cross-sectional area of the expanded stent is about 0.09 to about 0.16.