<p>The volumetric expansion–contraction behavior of heavy-section spheroidal graphite iron castings during solidification was examined via computer simulation to predict the existence of shrinkage cavities. To accurately grasp and quantify the expansion–contraction behavior, an actual solidification curve was divided into regions at the inflection points. And then, each region was given the theoretical amount of volumetric expansion and contraction according to a Fe–C system equilibrium diagram. The qualified values were adopted as the analytical factor for simulation software. The calculation results showed good matching to the actual shrinkage behavior such as the position and quantity.</p>