Biodiesel is a renewable and environmentally friendly fuel used in internal combustion engines. The major challenges in the biodiesel industry are those of food-fuel crisis associated with the use of edible oils for biodiesel production and the type of catalysts used for production. This work focused on the determination of optimal conditions for biodiesel production from inedible sandbox (Hura crepitans L.) seed using calcined snail shell (CSS) and potassium hydroxide (KOH) as catalysts. Oil was extracted from sandbox seeds using solvent extraction. The raw sandbox oil was used for biodiesel production using the transesterification method with KOH and CSS as catalysts. D-optimal design of response surface methodology (RSM) with 24 experimental runs was used to study the optimum yield response of biodiesel using temperature, time, and catalyst concentration as reaction the parameters. Selected fuel properties (specific gravity, viscosity, cloud point, pour point, density, and refractive index) of the ethyl esters were determined according to American Society for Testing Materials (ASTM) standards. The optimum biodiesel yield (93.97%) was obtained at residence time of 1 h 47 min and reaction temperature of 65 degrees C catalysts concentration (1.5 w/w). All the fuel properties determined fell within the specifications of ASTM standards.