The area of the site is . It is a chalk downland and thus part of the Dorset Downs. The site includes grassland, scrub and a small amount of woodland (mostly ash and oak, with a hazel and field maple understory); within the grassland there is a difference in character, and the species that it supports, which varies according to the gradient and aspect of the slopes. While the invertebrates on the site have not been extensively studied, it is known that species such as the rare Adonis blue and marsh fritillary butterflies can be found there; this is in addition to more common species such as the green hairstreak, common blue and gatekeeper. Fungi, particularly grassland varieties, are very well represented at Hog Cliff; the SSSI citation indicates over 60 genera as having been identified, whilst Natural England claim 100 species for the NNR. Cattle and sheep graze the site throughout the year to keep the grassland open.