The Carolina Wren is similar to the Bewick's and Marsh Wrens but has buffy, not white, underparts and rustier upperparts. House Wren has a less distinct supercilium, less rusty upperparts and barring on the belly and undertail coverts. Winter Wren is smaller, darker, has a shorter tail and less distinct supercilium.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.