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).
Tobias has been climbing in recent years. All-time it's been given to 29,322 U.S. babies, the 569th most common name by sound today, peaking at 1,523 in 2016, with 1,201 in 2025.
Tobias has no common alternate spellings by sound.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).