We present a scalable route to single-chain nanoparticles (SCNP) under mild conditions using intramolecular atom transfer radical coupling (ATRC). Typical methods to SCNP, a class of soft nanomaterials in the sub-10 nm size regime, rely on complicated synthetic techniques, high temperatures unsuitable to fragile functional groups, or ultradilute conditions (solutions less than 1 wt %), all of which greatly complicate scale-up. Our method uses a minimal number of synthetic steps and mild reaction conditions amenable to a wide array of solvents and tolerant to a variety of functional groups. Using this scalable method, gram quantities of nanoparticles in the 5-10 nm size regime are accessible.