Cephalometric Analysis Calculator

This calculator takes cephalometric angles and distances already measured from a traced lateral cephalogram -- not raw landmark coordinates -- and compares them to the classic Steiner/Downs/Wits normative values used in orthodontic diagnosis, with the SNA/SNB/ANB and FMA norms tracing back to Cecil Steiner's foundational 1953 paper "Cephalometrics for you and me": SNA 82 +/- 2 degrees, SNB 80 +/- 2 degrees, ANB 2 +/- 2 degrees, FMA 25 +/- 5 degrees, U1-NA 22 +/- 5 degrees / 4 +/- 2 mm, L1-NB 25 +/- 5 degrees / 4 +/- 2 mm, and a Wits appraisal of 0 mm for females / -1 mm for males (Jacobson's original norms). ANB is derived directly as SNA minus SNB and drives the skeletal classification: 0-4 degrees is Class I, above 4 is Class II (mandibular retrognathic), below 0 is Class III (mandibular prognathic). Because ANB is a straight subtraction, SNA and SNB affect it with exactly equal weight -- raising SNA by one degree raises ANB by one degree, and raising SNB by one degree lowers ANB by one degree, and neither input's declared range (both span exactly 25 degrees) gives either angle more leverage than the other.

Neither Class II nor Class III labels an etiology on their own: an elevated ANB is equally consistent with a retrognathic mandible or a prognathic maxilla, and a depressed ANB is equally consistent with a prognathic mandible or a retrognathic maxilla -- distinguishing which jaw is responsible requires reading the individual SNA and SNB deviations (or the Wits appraisal) rather than ANB alone, which is why this calculator labels both classes "(skeletal)" rather than naming a jaw. FMA, the incisor-to-NA/NB angles and distances, and the Wits appraisal are read independently for growth pattern and dental compensation but do not feed into ANB or the skeletal classification at all -- they describe vertical growth pattern and incisor position, a separate diagnostic dimension from the anteroposterior jaw relationship ANB captures. This tool checks arithmetic and normative comparison only; it cannot substitute for tracing accuracy, landmark identification, or a clinician's integration of the cephalometric analysis with models, photographs, and clinical exam.