The male Purple Finch is similar to the House Finch but lacks brown streaks on the breast and belly, has a more purple head, shorter forked tail and different call notes. Female House Finch lacks the distinctive face pattern of the female Purple Finch. Cassin's Finch is very similar in all plumages but has streaked undertail coverts and a larger bill. Male Cassin's has a brighter red crown. Female Cassin's has finer streaking on the breast and a less noticeable face pattern. Pine Siskin is similar to female but smaller and lacks face pattern. Sparrows are slimmer with longer tails and different markings.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.