Zero-age main-sequence radii and luminosities as analytic functions of mass and metallicity

We present fitting formulae for the zero-age main-sequence radii and luminosities of stars as functions of their masses and metallicities. The formulae cover masses from 0.1 to 100 M⊙ and metallicities from Z = 0.0001 to 0.03. Within this range the functions are everywhere strictly analytic. They take the form of rational functions in mass with only positive coefficients calculated as polynomials in metallicity. Errors are generally less than 7.5 per cent for luminosity and less than 5 per cent for radius. For a solar metallicity of Z = 0.02 these errors are less than 3 per cent for luminosity and 1.2 per cent for radius.