Solid line = floor (spellings that unambiguously belong to the group). Shaded band up to the dashed edge = ceiling (the most it could reach if every ambiguous spelling counted here).
Callie has stayed fairly steady in American naming for generations. All-time it's been given to 117,089 U.S. babies, the 277th most common name by sound today, peaking at 4,097 in 2014, with 2,647 in 2025.
By sound, Callie also includes the spellings Cali, Kallie, Kalli, Calli. Spellings sometimes heard the same way: Kali, Kalie.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).