Red deer during the rut on the Hoge Veluwe by Eric Wander

They are reddish-brown in summer and grey-brown in winter. The belly side is white and the tail is cream-coloured. Moulting starts first on the head, legs and front body. In September, the summer coat begins to give way to the winter coat, which is completely replaced by December. The summer coat returns in May and is complete in July or August.

The average body size of a red deer population is influenced by several factors. Red deer from forest areas are smaller than those from more open areas, and body size increases from west to east. Males are also larger than females. Head-rump length is between 165 and 260 centimetres, shoulder height between 114 and 140 centimetres. The tail, excluding the hair, is between 12 and 15 centimetres long, with hair about 20 centimetres. Males grow up to 255 kilograms in weight, females up to 150 kilograms.

Only the male carries antlers that average about 70 centimetres in length, but can grow to more than 90 centimetres. Its weight can range from four to 10 kilograms.[5] From the antlers, one can somewhat tell its age. A young red deer usually has smaller antlers with few branches, but a deer in its final stage of life will again have smaller antlers with fewer branches. A healthy animal will have heftier and heavier antlers, but not necessarily more scions than a sickly animal. There is a clear link between habitat quality and deer antler size.