What the Interior Design is and how it works

According to Council for Interior Design Qualification, “The range of possible scores is from 200 to 800 with the passing point being set at 500.”^[1]

The NCIDQ exam is run by the Council for Interior Design Qualification (CIDQ). It is the qualifying exam interior designers take to show they can protect health, safety and welfare in the spaces they design. The exam is split into separate sections: the IDFX, the IDIX and the IDPX. You can take each section at a Prometric test center or from home or office with remote proctoring (ProProctor).

The IDFX allows 3 hours, the IDIX 4 hours and the IDPX 3 hours. Your booked appointment is 30 minutes longer than the exam time. Scores run from 200 to 800, and 500 is the passing point. Official results are processed within 6 weeks after the testing period closes.

The exam fees are $305 for the IDFX, $470 for the IDIX and $365 for the IDPX. You also pay an application fee: $235 for Route 1, or $100 for Route 2 Part 1. Once your application is approved, Route 1 gives you 10 exam administrations (about 5 years) to pass, and Route 2 Part 1 gives you 4 administrations (about 2 years). Within that period you can retake as often as you need, but you can sit each section only once per administration.

Which route you qualify for depends on your education and work experience. Whether your state or province requires the certificate for registration or licensing also varies. Fees and rules can change, so check the current CIDQ Candidate Handbook on cidq.org before you apply.

Interior Design Exam at a Glance

What changed for Interior Design in 2026

• Oct 25, 2026: Delivery changed to Prometric test center or remote proctoring (ProProctor) (previously Computer-based via Prometric: test center or remote proctoring (ProProctor)).^[1]
• Oct 25, 2026: Exam fee (IDFX) changed to $305 exam fee (plus $235 Route 1 application fee, or $100 Route 2 Part 1) (previously $305 exam fee (plus application fee: $235 Route 1, or $100 Route 2 Part 1)).^[1]
• Oct 25, 2026: Retake policy changed to Unlimited retakes within the eligibility period; each section once per administration (previously Unlimited retakes within the eligibility period; each section at most once per administration).^[1]
• Oct 25, 2026: Validity changed to 10 administrations (~5 years) Route 1; 4 administrations (~2 years) Route 2 Part 1 (previously Eligibility lasts 10 administrations (~5 years) for Route 1, 4 administrations (~2 years) for Route 2 Part 1).^[1]

Worked examples: how to reason through Interior Design questions

These are practice questions written for this site, not questions from the real exam. Each explanation shows why the right answer is right and why the others are wrong.

Example 1

Question: Which color mode should a designer use when creating interior design graphics intended for screen display rather than printing?

1. RGB
2. CMYK
3. Pantone spot color
4. Grayscale

Answer: A. RGB

Explanation:

RGB is correct. Screens make colour by adding red, green and blue light. A graphic built in RGB matches what a monitor, tablet or projector can actually show.

• CMYK is the subtractive model for printing with cyan, magenta, yellow and black inks. Using it for screen work narrows the colour range and can make finishes look dull.
• Pantone spot colour is a named ink reference for consistent printed or manufactured colour. It is not a mode that a screen displays.
• Grayscale removes colour entirely, which defeats the point of presenting palettes and finishes.

Rule to remember: use RGB for anything viewed on a screen and CMYK for anything sent to a printer. When the output changes, convert a copy and keep the original file.

Example 2

Question: In textile specification, what does the term 'double rub count' measure?

1. Thread count per inch
2. Fabric abrasion resistance and durability
3. Colorfastness under UV exposure
4. Flame spread rating

Answer: B. Fabric abrasion resistance and durability

Explanation:

Fabric abrasion resistance and durability is correct. Double rubs come from abrasion testing. A fabric sample is rubbed back and forth until it shows visible wear, and each back-and-forth pass counts as a double rub. A higher count means the textile should hold up better under heavy use, which matters for contract seating.

• Thread count measures how densely a fabric is woven, not how it wears.
• Colorfastness under UV exposure is a separate test of fading.
• Flame spread is a fire-performance property set by flammability tests and codes, not by abrasion testing.

Rule to remember: abrasion tests (double rubs) measure durability, lightfastness tests measure fading, and flammability tests measure fire safety. A specification has to check each one separately.

Example 3

Question: How should an Interior Design professional handle a situation outside their scope of competency?

1. Attempt it anyway
2. Recognize limitations and refer to or consult with appropriate specialists
3. Ignore the situation
4. Decline all unfamiliar work

Answer: B. Recognize limitations and refer to or consult with appropriate specialists

Explanation:

Recognizing your limitations and consulting or referring to a specialist is correct. It protects the client and the public, which is why it is the professional standard.

• Attempting it anyway risks unsafe or noncompliant work and can breach professional ethics.
• Ignoring the situation leaves a known risk unmanaged and fails your duty to the client.
• Declining all unfamiliar work goes too far. Designers routinely coordinate with engineers, architects, code consultants and other specialists, and a referral or consultation lets the project continue safely.

Rule to remember: when a task falls outside your training or legal scope, say so, then consult or refer, and record the decision in the project file.

How to use these practice tests

Start with the CIDQ Candidate Handbook. Confirm which section you are taking, its time limit and your testing window. Then take the Interior Design Practice Test without notes to see where you stand.

• List the topics you missed and work through the matching sets, such as Regulatory Frameworks and Compliance, Space Planning and Ergonomics, Materials and Finishes and Lighting Design and Illumination.
• For every wrong answer, write a short rule in your own words, like the rules at the end of the worked examples above. Review these rules each week.
• Use Case Studies and Practical Application to practise weighing codes, budget and client needs together.
• For practice and ethics topics, add Professional Standards, Risk Assessment and Management and Communication and Stakeholder Relations.
• In the last weeks before your exam, do timed mixed sessions as long as your section (3 hours for the IDFX and IDPX, 4 hours for the IDIX) to build stamina.

Our questions are practice for recall and reasoning. Use CIDQ's official materials to confirm what each section covers.

Sources & last verified

1. Council for Interior Design Qualification — time limit, passing score, exam fee, retake policy (official source). “The duration of an exam appointment indicated in the confirmation email is 30 minutes longer than the time allotted to take the exam.” Verified Oct 25, 2026.

How we verify: editorial & fact-checking policy. Report an error: contact us.