ANB angle and Wits appraisal explained: what they measure and why they disagree

Simplified Orthodontics Academy · Published 26 October 2026

What the ANB angle measures

Two angles at nasion come first. SNA is the angle between the S-N line and the line from nasion to A point. SNB is the angle between S-N and the line from nasion to B point. They describe the front-to-back position of the maxillary and mandibular apical bases relative to S-N, a reference plane used by Riedel [1].

ANB is SNA minus SNB, which is the same as the angle between N-A and N-B. It compares the two apical bases with each other, as seen from nasion. Steiner gave 2° as the mean value [2].

• A positive ANB means A point lies ahead of B point, seen from nasion. The larger the angle, the further ahead.
• A negative ANB means B point lies ahead of A point.

Larger values are usually described as a tendency toward a Class II jaw relationship, and smaller or negative values as a tendency toward Class III. The Steiner analysis article shows ANB with the other Steiner readings.

What the Wits appraisal measures

Jacobson described the Wits appraisal in 1975 as another way to judge how the jaws relate to each other. It avoids nasion: instead, it uses the occlusal plane [3].

1. Draw the occlusal plane.
2. Drop a perpendicular from A point to the plane. Where it meets the plane is AO.
3. Drop a perpendicular from B point to the plane. Where it meets the plane is BO.
4. Measure the distance from AO to BO along the plane, in millimetres. It is positive when AO lies ahead of BO, and negative when BO lies ahead of AO.

In Jacobson’s sample of adults with excellent occlusion, AO and BO coincided on average in females, and BO was 1 mm ahead of AO in males [3]. These are the reference values Simplified Ceph shows: 0 mm for females and −1 mm for males. Jacobson later reviewed the appraisal in an update [4].

Simplified Ceph reads Wits on the functional occlusal plane, drawn through the cusp overlap of the first molars and of the first premolars.

Reading them side by side

Both readings answer the same question: how far is A point ahead of or behind B point? ANB answers it as an angle at nasion. Wits answers it as a distance along the occlusal plane.

When both are close to their reference values, or both are well above, or both well below, they agree. When one is close to its reference value and the other is not, at least one of them is being changed by something other than the relationship between the jaws. The next section explains what can do that. Neither reading is a diagnosis on its own.

Why ANB and Wits can disagree

The position of nasion

ANB is measured at nasion. If nasion lies further forward or further back, the angle changes, although A and B have not moved. Hussels and Nanda described the front-to-back position of nasion as one of the factors that change ANB [5]. Wits does not use nasion, so it does not change.

The position of the maxilla

Freeman showed that the position of the maxilla relative to the cranial base affects ANB on top of the relationship between the apical bases, and that the two effects can cancel each other or add up [6]. So the same ANB can come from different combinations of maxillary position and jaw relationship.

The inclination of the jaws

Hussels and Nanda also described how ANB depends on geometric factors, including the position of nasion, rotation of the jaws, facial height and dental height [5]. Part of this is simple geometry: the further A and B lie from nasion, the smaller the angle that the same front-to-back distance between them makes at nasion.

The occlusal plane

Wits depends on the occlusal plane. A and B lie one above the other, so when the plane tilts, AO and BO slide along it by different amounts (Figure 2). In geometric terms, the Wits reading equals the distance from A to B multiplied by the cosine of the angle between the line A-B and the occlusal plane. The plane is drawn through the teeth, so the position of the teeth affects the reading as well as the jaws. ANB does not use the occlusal plane at all.

Worked example

This example is a drawing, not a patient. We placed S, N, A and B on a schematic tracing with S-N 70 mm long: SNA 82° and SNB 79°, so ANB is 3°. With the occlusal plane at 14° to S-N, Wits is +0.8 mm. Then we changed one thing at a time, left A and B where they were, and measured again.

1. Moving nasion alone took ANB from 0.8° to 5.2°, on either side of Steiner’s 2°, while Wits stayed at +0.8 mm.
2. Tilting the occlusal plane alone took Wits from −2.7 mm to +4.3 mm, on either side of the reference values of 0 and −1 mm, while ANB stayed at 3°.
3. In this drawing B lies about 39 mm below A, so each 5° of tilt moved the Wits reading by about 3.5 mm.

The jaws never moved, yet each reading could be pushed above or below its reference value. Reading both, and knowing what each depends on, shows which one is likely to be misleading in a given tracing.

Limits

• Landmarks are placed by eye. A point, B point and the points of the occlusal plane are judged on the radiograph, so a small difference in placement changes both readings. The cephalometric landmarks article covers identification error.
• Which occlusal plane. Wits read on a different definition of the occlusal plane gives a different value, for the reason shown in Figure 2. Compare readings taken on the same plane.
• Reference values come from particular samples. Steiner gave his values as a guide to be adjusted for the individual, as the Steiner analysis article explains [2]; Jacobson’s values come from adults with excellent occlusion [3]. Most reference values come from specific study groups, so read them with the patient’s age, sex and ethnic background in mind.
• Description, not decision. This article describes the two measurements. It does not cover diagnosis or treatment planning.

Educational content for clinicians and students. Reference values vary between populations. This page does not replace clinical judgement.

References

1. Riedel RA. The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod. 1952;22(3):142-145. doi: 10.1043/0003-3219(1952)022<0142:TROMST>2.0.CO;2
2. Steiner CC. Cephalometrics in clinical practice. Angle Orthod. 1959;29(1):8-29. Publisher’s page
3. Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod. 1975;67(2):125-38. doi: 10.1016/0002-9416(75)90065-2. PMID: 1054214
4. Jacobson A. Update on the Wits appraisal. Angle Orthod. 1988;58(3):205-219. doi: 10.1043/0003-3219(1988)058<0205:UOTWA>2.0.CO;2
5. Hussels W, Nanda RS. Analysis of factors affecting angle ANB. Am J Orthod. 1984;85(5):411-23. doi: 10.1016/0002-9416(84)90162-3. PMID: 6586080
6. Freeman R. Adjusting A-N-B angles to reflect the effect of maxillary position. Angle Orthod. 1981;51(2):162-171. doi: 10.1043/0003-3219(1981)051<0162:AAATRT>2.0.CO;2

More to read

• Cephalometric analysis in Simplified CephSteiner, Wits and the other analyses in the tool
• Steiner analysis explainedSNA, SNB, ANB and the other Steiner readings, with their sources
• Cephalometric landmarks explainedThe main points and reference lines, and sources of identification error
• All articlesOrthodontic analyses, explained