Colby has been given to about 58,155 people in the United States since 1880. It was most common in 2001, which makes it a millennial-parent name.
Colby ranks 615th among American boys in 2025, with 515 born that year. Its best year was 2001, when 3,979 babies were given the name, ranking 99th. The typical living American called Colby is about 25 years old today. It is relatively most common in West Virginia, where it accounts for 0.07% of births.
Source: US Social Security Administration, national and state name files, 2025 release, and the Office for National Statistics for England and Wales. Etymology researched and written by our editors. Living-population and median-age figures are our own estimates, described in the methodology.