A theoretical picture describing the tensile strength σ_{T} of elastomers is developed. σ_{T} is composed of three factors: (1) the tensile strength of individual polymer load-bearing chains (LBCs) according to Eyring's theory, (2) an occupation number of LBC states using Fermi statistics, and (3) an excluded volume factor reducing the number of possible LBCs due to the presence of filler particles or crosslinks between polymers. This description is compared to experimental tensile strengths of carbon black (N339)-filled EPDM (Keltan 4450) as well as to other experiments in the literature studying the effects of temperature, filler concentration, and particle size as well as crosslink density.