We present a very simple polymer model of polyethylene glycols/oxides in water that can be used in combination with Molecular Dynamics or Monte Carlo simulations to accurately reproduce the equation of state and radii of gyrations across several orders of magnitude, in terms of osmotic pressure and polymer length. This is of importance for example in osmotic stress experiments, with the aim to accurately probe macromolecular interactions, although the polymer model may prove useful in many other scenarios as well. It is constructed in a manner that makes it straightforward to treat by classical density functional theory, which should facilitate theoretical studies of model systems with explicit polymers of realistic lengths and concentrations. The polymer model is validated by comparisons with experiments and a single-parameter equation of state by Cohen et al. From a computational perspective, we recommend Metropolis Monte Carlo simulations in the low concentration regime, whereas Molecular Dynamics simulations are preferable in the more concentrated systems, at least if one has access to computer clusters. (C) 2015 Elsevier Ltd. All rights reserved.