The ideal size depends on the breed and number of horses. For most full-sized horses, each stall should be at least 12′ x 12′. Larger breeds like draft horses may require 14′ x 14′. Aisles should be 10’–12′ wide for safe movement. Include extra space for tack rooms, wash bays, feed storage, and future expansion. A 4-stall barn with a center aisle, tack room, and storage typically ranges from 36′ x 48′ to 40′ x 60′.