- You need 70% correct out of 100 questions to pass the MD-MHVACR exam.
- That means roughly 70 correct answers within the 4-hour computer-delivered session.
- The exam is open-book, but only specific approved references are allowed - no study guides.
- A failed attempt means a 30-day wait before your first retest; later retests require 60 days.
The Number You Actually Need
If you're preparing for the Maryland Master HVACR Contractor License Exam, the passing score is simple to state and harder to guarantee: 70%. Administered by the Maryland Board of Heating, Ventilation, Air Conditioning and Refrigeration Contractors through PSI, the exam consists of 100 multiple-choice questions, which means you need approximately 70 correct answers to earn your Master license eligibility. There's no domain-by-domain minimum published - it's an overall score - but that doesn't mean you can ignore weaker domains and coast on strong ones. A 30-question gap in Refrigeration and Air Conditioning, the largest content area, is much harder to make up elsewhere than a gap in a smaller domain like Piping.
For a full walkthrough of everything the license requires beyond the score itself - experience hours, employer sign-off, and reference documentation - see our MD-MHVACR requirements guide. If you haven't yet confirmed you meet the three-year experience and 1,875-hour thresholds, that's the place to start before you even think about scheduling.
Exam Format: 100 Questions, 4 Hours, Open-Book
Understanding the mechanics of the test matters as much as understanding the content, because pacing errors are one of the most common ways candidates lose points they actually knew how to answer. The exam is:
- Computer-delivered through PSI testing centers
- 100 multiple-choice questions
- 4-hour time limit
- Open-book, with a defined list of approved references
- $150 examination fee
Four hours for 100 questions gives you roughly 2.4 minutes per question - generous compared to closed-book licensing exams, but the open-book format eats into that time if you don't already know your references cold. Candidates who plan to flip through Modern Refrigeration and Air Conditioning or the International Mechanical Code for every question will run out of time long before they run out of questions. The open-book allowance is a safety net for verifying code sections and formulas, not a substitute for actually knowing the material.
Key Takeaway
Treat the 4-hour window as a pacing budget: aim to have 50 questions answered by the halfway point, leaving buffer time for the harder Refrigeration and Air Conditioning and Heating Systems items later in the test.
How the Passing Score Interacts With the Six Domains
The 70% threshold applies to your overall score, but your prep plan should still be built domain by domain. The six content areas are:
Domain 1: Electrical Knowledge, Motors, and Controls
Covers wiring, motor types, control circuits, and troubleshooting logic that shows up throughout HVACR systems.
- Know control sequences, not just component names
Domain 2: Piping
Sizing, materials, and installation practices for refrigerant and system piping.
- Be able to apply code references quickly under time pressure
Domain 3: Refrigeration and Air Conditioning
The largest domain on the exam. Covers refrigeration cycles, system components, charging, and AC-specific troubleshooting.
- Allocate the most study hours here - it carries the most questions
Domain 4: Heating Systems
Furnaces, boilers, combustion, and heating equipment installation and service.
- Cross-reference Modern Refrigeration and Air Conditioning for combustion topics
Domain 5: Air Distribution Systems
Ductwork design, airflow calculations, and the ACCA Ductulator's practical use.
- Practice Ductulator problems by hand before test day
Domain 6: Safety
OSHA 29 CFR Part 1926 standards and general jobsite safety practices.
- Know where safety rules intersect with equipment-specific procedures
Because Refrigeration and Air Conditioning is confirmed as the largest domain, it has an outsized influence on whether you clear the 70% line. A candidate who is weak in this domain but strong everywhere else faces a much steeper climb than one who is weak in a smaller domain like Piping. For a deeper breakdown of every domain's scope and how questions are typically structured, read the complete guide to all six content areas.
Why "Open-Book" Doesn't Mean Easy
The open-book format is one of the most misunderstood aspects of this exam. Candidates sometimes assume that because they can bring references, the 70% passing score is easier to hit than a closed-book test. In practice, the opposite dynamic often plays out: the reference list is long, tabbing rules are strict, and the clock keeps running whether you're searching for an answer or writing one down.
Approved references include:
- 2012 or 2018 International Mechanical Code
- Modern Refrigeration and Air Conditioning, editions 19 through 21
- Manual J, 2006 eighth edition
- OSHA 29 CFR Part 1926
- An ACCA Ductulator
You're allowed to permanently tab, highlight, and underline these references, but handwritten notes and loose papers are prohibited, and study guides cannot be brought into the testing room at all. This means your reference prep has to happen well before test day - building your tab system is part of your study plan, not something you improvise during the exam. Our study guide for passing on your first attempt walks through how to build a tabbing system that actually saves you time under the clock.
If you're still deciding how much weight to give the open-book advantage in your overall prep, our difficulty guide breaks down where candidates tend to lose the most time and points despite having references in hand.
What Happens If You Miss 70%
Falling short of 70% is not the end of the road, but it does cost you time and money. After a failed attempt:
- Your first retest requires a 30-day wait before you can sit again
- Any subsequent retest requires a 60-day wait
- You'll pay the $150 exam fee again each time you retest
This waiting-period structure is a strong argument for treating your first attempt as the one that counts. A near-miss score - say, 60 or 65 correct - often means the gap wasn't a knowledge deficit but a pacing or reference-navigation problem, which is exactly what focused practice testing is designed to fix. For a closer look at how candidates historically perform and where the common failure points sit, see our pass rate analysis.
Key Takeaway
A 30-to-60 day retest wait plus another $150 fee makes a single well-prepared attempt far cheaper than two rushed ones. Budget your study timeline accordingly.
Scheduling Your Prep Around the Score Target
Because the passing score is fixed at 70% regardless of which domains you're strongest in, your prep schedule should be weighted toward the domains with the most questions and the ones you're least confident in - usually Refrigeration and Air Conditioning first, then whichever of the remaining five domains feels shakiest.
Refrigeration and Air Conditioning
- Review refrigeration cycle fundamentals and system components
- Build reference tabs in Modern Refrigeration and Air Conditioning
Electrical Knowledge, Motors, and Controls + Heating Systems
- Work through control circuit scenarios
- Cross-check combustion topics against your code references
Piping and Air Distribution Systems
- Practice Ductulator calculations by hand
- Tab International Mechanical Code sections on piping sizing
Safety and Full Timed Practice
- Review OSHA 29 CFR Part 1926 key sections
- Run full 100-question, 4-hour timed practice sessions
Timed practice tests, taken with your actual tabbed references, are the single best way to simulate the real pressure of hitting 70% inside four hours. You can run through full-length practice tests to build both content knowledge and pacing before you commit to a real exam date. Once your practice scores are consistently clearing 70% with margin to spare, you're in position to lock in a testing date - our exam dates and scheduling guide covers how PSI scheduling windows work in practice.
What a Failed Attempt Actually Costs You
The passing score isn't just an academic number - it has real financial weight attached to it. Here's how the costs stack up around a single attempt versus a retest scenario:
| Item | Cost / Requirement |
|---|---|
| Exam fee (per attempt) | $150 |
| Passing score required | 70% (70 of 100 questions) |
| Wait after first failed attempt | 30 days |
| Wait after subsequent failed attempts | 60 days |
| Master license fee (after passing) | $94.50 |
Beyond the exam fee itself, Master Contractors subject to the insurance requirement must also maintain $300,000 in general-liability insurance and $100,000 in property-damage insurance - costs that sit alongside your licensing fees once you're operating under the Master credential. For the full financial picture, including what happens if you're pursuing reciprocity with Delaware or Virginia instead of testing fresh, check out our complete pricing breakdown.
It's also worth stepping back and asking whether the investment of time, fees, and insurance obligations pays off relative to your career goals - our ROI analysis and salary guide both address that question directly using the facts specific to this Maryland credential, not generalized industry averages.
FAQ
You need 70% correct on the 100-question multiple-choice exam, which works out to approximately 70 correct answers.
No. The 70% threshold applies to your overall score across all six domains, not to each domain individually. However, since Refrigeration and Air Conditioning is the largest domain, weak performance there has the biggest impact on your total.
No. Approved references may be tabbed, highlighted, and underlined, but handwritten notes and loose papers are not allowed, and study guides are prohibited entirely.
Your first retest requires a 30-day wait. Any subsequent retest requires a 60-day wait, and you'll need to pay the $150 exam fee again each time.
Not necessarily. The reference list is limited and specific, and searching through books during a timed 100-question exam can cost more time than it saves if you haven't practiced navigating your tabbed references in advance.
Hitting 70% on the MD-MHVACR exam comes down to knowing exactly which domain carries the most weight, having your approved references tabbed and ready before you sit down, and pacing yourself across the full 4-hour window. For a condensed, at-a-glance review of the facts covered here, bookmark our one-page cheat sheet and revisit it in the days before your test date.