Designing dies for sheet and film extrusion presents the primary challenge of achieving a uniform velocity distribution at the die exit, which is crucial for minimizing thickness variation in the extruded product. For multilayer coextruded sheets and films, there is an additional challenge of maintaining a consistent layer thickness across the extruded polymer. In sheet and cast film extrusion, a flat die with a coat-hanger-shaped manifold is commonly employed. The manifold ensures uniform velocity at the exit by effectively distributing the polymer across the die. Blown films, on the other hand, are extruded using a spiral mandrel annular die. The spiral groove in the mandrel overlaps multiple melt streams, eliminating weld lines and promoting circumferential flow uniformity. Flow simulation software, capable of accurately predicting velocity, pressure, temperature distributions, and layer structures in extruded sheets and films, serves as a powerful tool for designers of both coat-hanger and spiral mandrel dies. Unlike profile extrusion dies, which are highly customized, the geometries of coat-hanger and spiral-mandrel dies are well-established in the literature and can be easily parameterized using 3D CAD software like SolidWorks or Autodesk Inventor. As a result, die optimization software, which can automatically determine optimal values of the geometric parameters, can significantly accelerate die development for sheet and film extrusion. This presentation will discuss key design parameters for coat-hanger manifold and spiral mandrel dies. The polyXtrue software is utilized to accurately predict the velocity, pressure, temperature, and layer structure in the dies. Furthermore, die geometries for both coat-hanger manifold sheet dies and spiral mandrel blown film dies are optimized using the optiXtrue software. Results from these flow simulations and die optimizations will be presented and analyzed