API 653 Aboveground Storage Tank Inspector Certification
The credential for inspectors of aboveground storage tanks — shells, bottoms, foundations, repairs, reconstruction and hydrotests.
About the exam
API 653 certifies inspectors of aboveground atmospheric storage tanks built to API 650 and API 12C. It shows you can evaluate corroded shells and bottoms, judge settlement, set inspection intervals, recognize damage mechanisms, review welding and NDE, and control repairs, alterations and reconstruction under API 653.
The closed-book section tests everyday working knowledge: tank inspection practices from API RP 575, damage mechanisms, cathodic protection (RP 651), bottom linings (RP 652), welding and NDE. The open-book section shows the codes on screen for calculations and look-ups: corrosion rates and intervals, shell minimum thickness and maximum fill height, corroded-area averaging and pitting, bottom minimum remaining thickness, settlement, impact testing, hot-tap spacing, patch and replacement plates, and nozzle weld sizes.
Our practice follows API's effectivity sheet for the March to November 2027 exams: API 653 5th edition with Addenda 1–4 (Addendum 4, July 2025), API 650 14th edition (August 2025), API RP 575 5th edition with Addenda 1–2, RP 576 5th edition (selected sections), RP 577 3rd edition, RP 651 5th edition (2024), RP 652 6th edition (2025), RP 571 3rd edition (10 named mechanisms) and the 2025 ASME BPVC Sections V and IX. The November 2026 window still uses API 650 13th edition and the 2023 BPVC.
How we track your progress
Every blueprint domain moves through five levels as you study:
- Not startedNo questions answered in this domain yet.
- Getting startedFirst questions answered — not enough yet to judge.
- DevelopingAt least 5 answered and 50% or better on your recent questions.
- ProficientAt least 15 answered and 70% or better on your recent questions.
- Exam readyAt least 25 answered, 80% or better recently, and holding up on hard questions.
The exam blueprint
API 653 Body of Knowledge and Publications Effectivity Sheet for the March, July and November 2027 exams — 170 items (140 scored, 30 pretest): 110 closed-book, 60 open-book across 8 Body of Knowledge areas; weights are QuizMe estimates. Tap a domain to see its topics.
1 Tank inspection practices and intervals about 16% (est.) of the exam
56 practice questions in this domain so far
2 Shell evaluation and calculations about 15% (est.) of the exam
52 practice questions in this domain so far
3 Bottoms, foundations and settlement about 13% (est.) of the exam
44 practice questions in this domain so far
4 Damage mechanisms and corrosion control about 12% (est.) of the exam
40 practice questions in this domain so far
5 Welding: ASME IX, API 577 and tank welding rules about 13% (est.) of the exam
44 practice questions in this domain so far
6 NDE and examination requirements about 9% (est.) of the exam
32 practice questions in this domain so far
7 Repair, alteration, reconstruction and hydrotest about 14% (est.) of the exam
48 practice questions in this domain so far
8 API 650 design, materials and brittle fracture about 7% (est.) of the exam
24 practice questions in this domain so far
What you get when you access this exam
Free with your QuizMe account.
Inspector scenarios aligned to the Body of Knowledge
Every question is tagged to one of the 8 API 653 areas and its topics — shell thickness and fill height, bottom MRT, settlement, damage mechanisms, WPS/PQR review and what the inspector does next.
Exam-critical hints
Reveal the code concept that unlocks the question — the formula, the governing rule, the value that matters. Every answer comes with the full rationale and worked solution.
Adaptive testing
Questions steer toward your weakest areas, weighted by our estimate of how much each counts on the real exam, and get harder as you get stronger.
Timed practice exams
Full-length exams at the real pace — 170 questions in 6.5 hours of testing — with a live pacing indicator and a full review.
Flashcards, case simulations and guides
100 flashcards for damage mechanisms, tank terms and formulas, 6 inspection cases where a tank's shell, bottom and settlement data and repair decisions unfold step by step, and interactive illustrated guides you explore hotspot by hotspot.
Progress for every blueprint area
Each area moves from Not started to Getting started, Developing, Proficient and Exam ready — so you know exactly what to study next.
Test at home or at a center
Apply through API's ICP portal by the deadline for your chosen window. Once approved, you get an authorization to schedule your API 653 exam with Prometric on any open day inside that window. The next windows are March 12–April 2, 2027 (apply by January 7, 2027) and July 9–30, 2027 (apply by May 6, 2027).
At a Prometric test center
- API 653 is offered in person only — API stopped remote testing for 510, 570, 653 and 1169 in September 2024.
- Bring government-issued photo ID; the name must match your API account exactly.
- No papers or code books in the room. A calculator, scratch paper and pencil are provided, and an on-screen calculator is built in.
- Phones, watches, bags and notes go in a locker.
Before you book
- Your application is valid for 12 months from the first window you request; moving to a different window means a new application and fees.
- Prometric rescheduling inside a window: free 60+ days out, $35 at 30–60 days, $70 at 5–29 days, not allowed under 5 days.
- Buy or borrow the exact code editions on the effectivity sheet and study from them — the exam shows those PDFs, not your copies.
- Work through API's exam tutorial so the on-screen PDF viewer isn't new on exam day.
Exam-day game plan
How to walk in ready — and how to pace 170 questions in 6.5 hours.
Pacing checkpoints
Hit these and you finish with time to revisit your flagged questions. Our timed practice exams run at this same pace.
The week before
- Take one full-length timed practice exam 3–5 days out, then rest.
- Spend your last sessions on the heaviest areas — inspection practices, shell evaluation and repairs — plus anything still below Proficient.
- Rework every calculation type in the Body of Knowledge from a blank page, in both US customary and SI units.
- Practise finding paragraphs in the effectivity-sheet editions using bookmarks and the table of contents, not memory.
Exam morning
- Eat a real breakfast; the day runs about 7.5 hours with one 45-minute lunch break.
- Arrive 30 minutes early at the Prometric center with ID that matches your API account.
- Use the restroom right before you start.
During the exam
- The first section is closed-book: 110 questions in 2 hours 45 minutes. Answer everything before you click Finish — you can't come back.
- After the break, the open-book section shows the codes on screen: 60 questions in 3 hours 45 minutes, so there's time to look things up.
- Look up only what you need. Write down every given value, the formula and the units before you calculate.
- Check units: tank formulas mix feet and inches, and SI questions need the SI form of the equation.
- Answer every question — there's no penalty for guessing, and multiple-select items need every correct choice.
- 30 questions are unscored pretest items you can't identify.
Keep your head
- A few nerves sharpen focus. If you freeze, take three slow breaths and reread the stem.
- You're measured against a fixed standard, not other test-takers.
- Change an answer only when you find a real reason in the stem or the code.
Keeping your API 653 certification
- Certification lasts 3 years.
- To recertify, show that at least 20% of your time over the 3 years was spent performing or supervising aboveground storage tank inspection.
- You also need 24 continuing professional development (CPD) hours per 3-year cycle, across at least two CPD categories.
- Every 6 years — every second recertification — you also pass API's online open-book quiz: 25 questions in 4 hours, two attempts. Fail twice and you must retake the full exam.
- Apply from 90 days before your expiration date; a 90-day late window carries extra fees.
Official sources and further reading
- API 653 Aboveground Storage Tank Inspector ↗The official program page: exam format, windows, eligibility and recertification.
- API 653 Body of Knowledge (March – Nov 2027) ↗Every topic, calculation and exclusion on the 2027 exams.
- API 653 Publications Effectivity Sheet (March – Nov 2027) ↗The exact code editions and sections in scope, including API 650 14th edition.
- API ICP — Schedules and fees ↗Exam windows, application deadlines and fees for every program.
- API ICP — Examinations ↗Scheduling with Prometric, scaled scoring and what you may bring.
- API — Exam tutorial for 510, 570 and 653 ↗How the closed-book and open-book sections and on-screen codes work.
- Prometric — American Petroleum Institute exams ↗Book, reschedule and find a test center.
Ready to start?
340 questions and scenarios across the blueprint — and growing.
API 510, API 570, API 653 and API 1169 are certification programs of the American Petroleum Institute. QuizMe and thinQtank Learning are not affiliated with or endorsed by API, ASME or Prometric. API and ASME codes and standards are copyrighted — candidates need their own copies of the editions on API's effectivity sheet, and our practice items are original, not recalled exam questions. Exam details are summarized from API's published Body of Knowledge, effectivity sheet and program pages; fees, dates and editions change — always confirm at api.org before you apply. Our domain weights are estimates; API publishes no percentages.