It is a medium-sized sparrow at and . It has a thick bill suited to eating seeds, which is black on the breeding male, horn-coloured on the non-breeding male, and yellowish with a dark tip on the female. Wingspans for males range between and those for females from . Tail, bill, and tarsus lengths are , , and , respectively. Measurements for the russet sparrow vary geographically, between the three subspecies, and also within the Himalayan subspecies cinnamomeus. The subspecies cinnamomeus is generally larger than the others, and within this form there is a tendency for birds at higher altitudes to be larger, and a clinal variation in size with the smallest birds in the west of the range and the largest in the east. The iris is chestnut in colour. The legs of both sexes are pale brown to pinkish-brown. The flight of all sparrows is swift, and that of the russet sparrow is described as swifter and more direct than that of the Eurasian tree sparrow. Plumage The sexes differ, or are dimorphic, in their plumage, and have a similar pattern to that in the corresponding sex of house sparrow. There is some variation between the three subspecies, especially in the colouration of the underparts. Birds of the subspecies rutilans are off-white on their cheeks and the sides of their necks, and have pale grey underparts. Birds of the subspecies intensior have a pale yellow wash on their underparts and cheeks, as well as darker upperparts, while those of the subspecies cinnamomeus have a heavy yellow tinge to their underparts. Moult is poorly recorded, the only records coming from Sakhalin and Himachal Pradesh. In Sakhalin, moult occurs in August and September, between the breeding season and migration. In Himachal Pradesh, aviculturalist G. A. Perreau observed captive and wild birds and reported that they were yellow from December to spring and whitish during the remainder of the year, a pattern which may be atypical. The breeding male is bright russet or cinnamon red on its upperparts from its crown to its rump, with a black streaking on its mantle. It has a small black bib and black around its eye, separated from the russet of its crown by a very thin white supercilium, a stripe running from the bill to the rear of the head. The side of its neck and cheek are off-white, and its underparts are pale