OAT vs DAT: Differences, Difficulty and Which Test You Take

Take the OAT if you are applying to optometry school and the DAT if you are applying to dental school. Both are administered by the same organization (the American Dental Association) and share nearly identical structure, but the OAT has a Physics section while the DAT has a Perceptual Ability Test that measures spatial reasoning. Each is required by its own set of professional schools, and you cannot substitute one for the other.

If you are still choosing between optometry and dentistry, or you have already picked a path and just want to know what the exam looks like, the good news is that the two tests overlap heavily. The natural science content is essentially the same. Below is a side by side breakdown, followed by answers to the questions applicants actually ask.

OAT vs DAT at a glance

How the two exams are built

The OAT is 230 multiple choice questions split across four tests. The Survey of the Natural Sciences carries 100 questions (40 Biology, 30 General Chemistry, 30 Organic Chemistry). Reading Comprehension adds 50 questions, Physics adds 40, and Quantitative Reasoning adds 40. Everything is scored on a 200 to 400 scale where 300 sits at the 50th percentile, so a 300 is dead average. You also get an Academic Average, which combines your scores across the six subject areas. A competitive OAT is roughly 320 and up, which puts you comfortably above the median.

The DAT is 280 multiple choice questions across four sections. It shares the same 100 question Survey of Natural Sciences (Biology, General Chemistry, Organic Chemistry), the same 50 question Reading Comprehension, and the same 40 question Quantitative Reasoning. The difference is the Perceptual Ability Test, a 90 question section on spatial reasoning: folding shapes, reading angles, counting hidden cubes and mentally rotating objects. Since March 1, 2025 the DAT uses a new 200 to 600 scale where about 400 is average and 420 and up is competitive. If you took an older DAT, do not compare your number directly to the new scale.

Because the Survey section is basically identical and both tests include the same reading and quantitative sections, the content overlap is high. The Physics versus Perceptual Ability swap is the one real fork in the road.

It is worth pausing on the Reading Comprehension and Quantitative Reasoning sections, since they behave the same on both exams. Reading Comprehension gives you dense science passages and 50 questions that test whether you can find and interpret information under time pressure, not whether you already knew the topic. Quantitative Reasoning is 40 questions of applied math: algebra, fractions, ratios, basic trig and word problems. Neither section requires new coursework, but both reward timed practice, because the challenge is pacing rather than difficulty. Students who bomb these sections usually ran out of time, not knowledge.

Is the OAT harder than the DAT?

Neither test is objectively harder; they are hard in different places. The OAT swaps in Physics, which rewards students who are comfortable with formulas, units and quick problem setup. If you liked your physics coursework, that section can be a scoring asset. The DAT swaps in Perceptual Ability, which is unlike anything most students see in a lecture hall. Spatial reasoning is trainable, but it feels foreign at first and many test takers underestimate how much practice it takes to get fast.

So the honest answer is that the OAT feels harder to people who struggle with physics, and the DAT feels harder to people who struggle with spatial visualization. The shared science load is the same for both, so your relative difficulty comes down to which unique section suits your brain. Total testing time is also a touch longer on the OAT, at about five hours versus roughly four hours and fifteen minutes, which matters for stamina.

One thing that trips up applicants is comparing raw scores. A 320 on the OAT and a 420 on the DAT are competitive numbers, but they live on completely different scales, so a bigger number does not mean a harder test or a stronger performance. The OAT tops out at 400 with 300 as the exact median, while the DAT now runs 200 to 600 after the March 2025 change. Judge yourself against percentiles and the average admitted scores at your target programs, not against a friend on the other track.

Can I take one test for both optometry and dental school?

No. There is no combined exam. If you are applying to optometry programs you take the OAT, and if you are applying to dental programs you take the DAT. Some students who are genuinely undecided end up sitting for both, but that means preparing for two separate exams, paying two separate fees and building spatial reasoning skills for the DAT that the OAT never asks about. Most advisors will tell you to commit to a path first, then prepare for the one test that path requires.

Do dental and optometry schools accept each other's test?

Generally no. Optometry schools require the OAT, and dental schools require the DAT. They are different professional tracks with different admissions committees, and each expects its own exam. The shared administration by the American Dental Association can make people assume the scores are interchangeable, but they are not. Always confirm requirements on the admissions page of each program you are targeting, since a small number of schools have their own policies, but plan on taking the specific test for your intended field.

How to study for the science sections

Here is where the overlap works in your favor. Whether you are prepping for the OAT or the DAT, the Survey of the Natural Sciences is the same 100 question beast covering Biology, General Chemistry and Organic Chemistry, so a strong science routine carries over almost entirely. This section is memorization heavy, which means active recall beats passive rereading by a wide margin. You want to be quizzed, not just to review.

The most efficient approach is to turn your own class notes and review books into practice questions, because questions drawn from the material you already studied hit exactly the facts your program emphasized. You can generate OAT practice questions from your own notes or build DAT practice questions from the same source files, then run through them in short daily sets. If your notes are on paper, you can scan your handwritten study notes into text first so they are easy to upload and reuse. That small step turns a semester of biology and chemistry scribbles into a searchable, quizzable bank.

A few study habits that pay off for both exams:

• Front load Organic Chemistry reactions and Biology terminology, since those are the highest yield memorization targets in the Survey section.
• Space your practice questions across days rather than cramming; spaced repetition locks in facts that a single long session will not.
• Track which subjects drag your Academic Average down and pour extra question sets into the weak spots.
• For the OAT, drill Physics formula recall so setup is automatic under time pressure.
• For the DAT, treat Perceptual Ability like a skill sport: short, frequent practice reps build the visualization speed you cannot memorize.

The bottom line

The OAT and DAT are close cousins built by the same organization, with the same core science, reading and math. Choose the OAT for optometry school and the DAT for dental school, and know that the deciding difference is Physics on the OAT versus Perceptual Ability on the DAT. Pick your profession, prepare for the one exam it requires, and lean on your own notes to master the science content that both tests share.