InflationEasy simulates the evolution of a scalar field during cosmological inflation on a three-dimensional lattice in an expanding Friedmann–Lemaître–Robertson–Walker (FLRW) universe. Written in C++ and inspired by and partially adapted from LATTICEEASY (ascl:1911.015), the code evolves the field on a cubic grid and computes the associated cosmological dynamics during inflation. It supports analytical or tabulated inflationary potentials and allows users to configure physical and numerical parameters through input files and header settings. InflationEasy produces outputs including field statistics, background quantities, scalar power spectra, and scalar-induced gravitational-wave spectra (from both inflation and post-inflation horizon re-entry), which can be analyzed using included post-processing tools such as Jupyter notebooks. Optional OpenMP parallelization accelerates simulations on multi-core systems.