Forty‑five fattening cattle (19 males and 26 females) have been studied. Skin area was established by photogrammetry techniques, and it was interpreted as a body surface area (BSA). Body weight was estimated from the hot carcass weight. BSA values obtained ranged from 2.55 to 8.12 m² (CV=38.5%) and they presented a higher significant correlation to body length (r_s=0.736) than to body weight (r_s=0.415). It was stablished the simple equation BSA (cm²)=(body length in cm) ², which showed a highly significant correlation with the actual area (r=0.913, p<0.0001). The estimated BSA by the formula proposed here underestimates the real area, since neither the skin of the distal parts and head were included in the skinning. Moreover it must not be applied to animals out of the age range considered (295‑396 days). In any way body length is much easier and safer to obtain in the field by the usual zoometric methods than weight.