The DAT and OAT are sibling exams -- both administered by the American Dental Association's Department of Testing Services, both computer-based at Prometric testing centers -- but they're built for different professional paths, and the differences matter if you're deciding between dentistry and optometry, or studying for both.
Section structure
The DAT has four sections: Survey of the Natural Sciences, the Perceptual Ability Test (a spatial/3D-rotation image-based section), Reading Comprehension, and Quantitative Reasoning. The OAT has four sections too, but swaps the DAT's Perceptual Ability Test for a full Physics section -- algebra-based, non-calculus introductory physics. This is the single biggest structural difference between the two exams: the DAT has no Physics content at all, and the OAT has no spatial/image-based section.
Related: What to Expect on the DAT: Format, Scoring, and How to Prepare
Survey of the Natural Sciences overlap
Here's the genuinely useful fact if you're studying for both: the Survey of the Natural Sciences section covers essentially the same topic breadth on both exams -- the same Biology, General Chemistry, and Organic Chemistry topic areas, in the same 40/30/30 question split. Strong prep in this section transfers directly between the two exams.
Quantitative Reasoning differences
Both exams provide a basic four-function calculator for their Quantitative Reasoning sections, and the topic areas and format are essentially identical. Like Survey of the Natural Sciences, prep here transfers well between the two exams.
Scoring scales
This is a common point of confusion: the DAT is scored 200-600 per section (as of March 1, 2025), while the OAT is scored 200-400 per section -- a genuinely different scale, despite sharing an administering body. Don't assume a "good DAT score" and a "good OAT score" look numerically similar; check the specific score expectations published by dental schools versus optometry schools separately.
Which exam do you actually need?
This isn't really a choice -- it's determined by which professional path you're pursuing. Dental school admissions require the DAT; optometry school admissions require the OAT. If you're genuinely exploring both paths and haven't decided, note that the Physics content on the OAT and the Perceptual Ability Test on the DAT each require dedicated prep time the other exam simply doesn't test -- factor that into your decision if timing or workload is a real constraint.