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).
Brianna has been slowly declining from its former popularity. All-time it's been given to 477,218 U.S. babies, the 316th most common name by sound today, peaking at 22,747 in 1996, with 1,982 in 2025.
By sound, Brianna also includes the spellings Briana, Breanna, Bryanna, Bryana, Brieanna, Breeanna. Spellings sometimes heard the same way: Breana.