API 510 Exam Day: Format, Timing and How to Pace It

The format, from API's own page

Everything in this section comes from API's API 510 certification page, read on 26 October 2026.

• The exam is given in person at designated test centers only.
• The exam day is 7.5 hours long. It has a short tutorial session, 2.75 hours for the closed-book part, a 45-minute lunch break and 3.75 hours for the open-book part.
• There are 170 questions, of which 140 are scored. The other 30 are pretest questions.
• There are 110 closed-book questions and 60 open-book questions.
• Papers, notes and books are not allowed in Prometric's computer testing centers. During the open-book part, PDF documents of the pertinent codes and standards are available on your computer, in English.
• Only the specific sections of each publication listed on the effectivity sheet are available to you during the open-book part.

API also posts an exam tutorial and asks you to view it before exam day. Do that, because the on-screen tools are the part you cannot practice from a book.

What the numbers mean per question

Simple division gives you the pace:

Two things follow. First, 1.5 minutes is tight for anything that needs a calculation, so closed-book math has to be a drill you have run many times. Second, 3.75 minutes is generous only if you know where to look. A single lookup that takes 6 minutes costs you the time of nearly two other questions.

Because 30 of the 170 are unscored pretest items and you cannot tell which, treat every question as if it counts.

A pacing plan for the closed-book part

The closed-book part is knowledge and everyday working familiarity, including the methods the Body of Knowledge says may be closed book: metal loss, corrosion rate, remaining service life and the inspection interval rules.

1. First pass at about 1 minute each. Answer what you know right away. Mark anything that needs more than a minute of arithmetic, using whatever way the exam software gives you to return to a question (the tutorial shows the tools).
2. Second pass for the marked calculations. Write the inputs first (readings and dates, required thickness, rate, units), then compute. Our calculation mistakes article explains why that habit is worth the seconds.
3. Leave a buffer. Aim to finish the first pass with about 30 minutes left, and spend it on the marked questions before you review the rest.

Before time runs out, check that every question has an answer selected. The exam asks you to choose the best answer from the options given, so a reasoned pick beats a gap.

A pacing plan for the open-book part

The open-book part uses more detailed information that you are expected to find in the documents but would not normally memorize.

1. Sort by lookup cost, not by order. A question that points to a table you know is a 2-minute question. A question that needs you to search three documents is a 6-minute question. Take the cheap ones first.
2. Set a cap. If a lookup passes 5 minutes, mark it, pick your best guess and move on.
3. Know the layout before you start. The PDFs are searchable on screen, but searching only helps if you know the right term. Practice with the sections on your window's effectivity sheet, using the section numbers from the Body of Knowledge as your map.
4. Do not trust a remembered edition. The exam is based on the editions on the effectivity sheet for your window, even if your employer or your state uses a different one.

The open-book strategy guide goes deeper on how to build that map.

Rehearse the whole day, not just the questions

Most people practice in 20-question sets. The exam is a seven-hour endurance task with a lunch break in the middle, so train for it.

• Run one long session. Two weeks before your window, do a half-day set of timed questions: 55 closed-book questions in 82 minutes is the same pace as the real part. Then, after a break, 30 open-book questions in 112 minutes.
• Practice on a screen. You will read stems and PDFs on a computer, so stop doing all your drills on paper.
• Plan the break. The 45-minute lunch is a reset. Eat, walk, and do not spend it reviewing the closed-book part you cannot change.
• Sort logistics early. The window deadline, the Prometric booking and any travel all need time. The schedule and fees guide lists the current windows and the six-month application rule.

What to do in the last week

Do not start new topics. Run a timed set, label each miss as method, setup, lookup or arithmetic, and fix the label you use most. Reread your own one-page summary of the closed-book methods. Confirm your appointment time and test center, and read API's exam day page for what to bring.

Next step

Take the free 10-question check at /api-510#q1 under a timer, so you can see your pace and your weak domains in a few minutes. Then see the plans at /api-510/offer#plans for timed practice exams, and ask Patch, the study buddy, at /study-assistant to turn your exam date into a week-by-week pacing plan.

FAQ

How many questions are on the API 510 exam?

API lists 170 questions, of which 140 are scored and the rest are pretest questions. There are 110 closed-book questions and 60 open-book questions.

How long is the API 510 exam?

API describes the exam day as 7.5 hours: a short tutorial, 2.75 hours for the closed-book part, a 45-minute lunch break and 3.75 hours for the open-book part.

Can I bring my own codebooks to the API 510 exam?

No. Papers, notes and books are not allowed in Prometric's testing centers. During the open-book part, PDF copies of the pertinent codes and standards are available on your computer, limited to the sections on the effectivity sheet.

Is the API 510 exam taken online?

No. API says the exam is administered in person at designated test centers only.

Sources

• API 510 Pressure Vessel Inspector: exam structure and what you can bring, American Petroleum Institute, read 26 October 2026
• API 510 Body of Knowledge, September 2026 to May 2027, American Petroleum Institute (closed-book and open-book descriptions, answer format)
• Pacing figures are our own arithmetic from API's published times and question counts.