The folding/collapse of linear single chains to single-chain nanoparticles (SCNPs) is a field of intense activity. Current synthetic methods allow obtaining from sparse SCNP morphologies in solution - resembling those observed in intrinsically disordered proteins - to compact SCNP conformations, more akin to those displayed by globular enzymes. A useful characterization technique in the field of SCNPs is conventional size-exclusion chromatography (SEC) with differential refractive index (DRI) detection, providing rapid and convincing evidence of SCNP formation through comparison of the SEC traces of the precursor and the SCNPs. Upon SCNP formation, a noticeable shift of the SEC curve toward longer retention times (i.e., lower hydrodynamic sizes) is observed. However, quantitative information embedded in the SEC curve about the actual compaction degree of the SCNPs has not yet been extracted to distinguish between sparse and globular SCNPs. Here, a useful methodology for quantifying the compaction degree of SCNPs by SEC with conventional DRI detector is introduced allowing: i) construction of theoretical SEC curves corresponding to the collapse of a linear precursor having a log-normal molecular weight distribution to either sparse or globular SCNPs and ii) analysis of experimental SEC curves to estimate the actual morphology of synthetic SCNPs in solution.