You can buy polystyrene foam blocks from various retailers depending on whether you need small craft sizes, large construction blocks, or bulk industrial quantities.

For specific densities or large "construction-grade" blocks, these specialized sellers are often more cost-effective.

These are the best options for quick, individual purchases for DIY or art projects.

& Lowe’s : While they primarily sell large insulation sheets (XPS "pink" or "blue" foam), these are frequently used by crafters who stack and laminate them to create thick blocks for carving. Online Marketplaces & Specialty Suppliers

: Carries a standard selection of white and green craft foam shapes and blocks.