Explorer — MetTutor · Free Metrology Learning
★ Free · Forever · No Credit Card

Explore the science that
measures everything.

“Curious about how the world is measured? You’re already a metrologist.”

Start Learning Free Compare all plans
MetTutor v2.0 · No account required to explore
950+
Standards & documents in MetLibrary
4
Learning modes, all included free
100%
Free · always, no expiry
5
Export formats: Word, Excel, PDF, CSV, TXT
Explorer Plan · Free

Everything you need to start

Explorer is a complete metrology learning platform — not a preview, not a trial. Free, unlimited, and ready the moment you sign up.

🤖
AI Metrology Tutor
Ask anything about metrology and receive detailed, expert-level answers drawn from authoritative standards. Unlimited questions, no message caps.
Unlimited messages
📚
MetLibrary Citations
Every answer MetTutor gives is grounded in the MetLibrary — 950+ curated metrology documents. You always see which standard your answer comes from.
950+ documents
🗺️
Metrology Skills Matrix
Navigate your learning journey with a structured map of metrology competencies — from fundamental measurement concepts to advanced calibration techniques.
Competency framework
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Concept of the Day
A fresh VIM vocabulary term every day, with a plain-language explanation and its role in measurement practice. Build your metrology vocabulary one term at a time.
VIM · JCGM 200:2012
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Voice Input & Read-Aloud
Ask questions by voice using your microphone. Have any answer read aloud at your pace. Learn while you work — hands-free.
Voice-enabled
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Full Export Suite
Export any MetTutor response to Word, Excel, PDF, CSV, or TXT — save your work, share answers with your team, or build study materials.
Word · Excel · PDF · CSV · TXT
Four Learning Modes

Ask it anything. It knows metrology.

MetTutor organizes learning into four focused modes so you always get the right kind of answer for what you’re trying to accomplish.

💡
Concept
Understand the science behind measurement — traceability, uncertainty, calibration principles, units of measure, and the international standards that govern them. Detailed explanations at the level you need.
What is traceability? Explain expanded uncertainty NIST SI base units
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Problems
Work through numerical metrology problems step by step. Unit conversions, TUR calculations, uncertainty budgets — MetTutor walks you through the method, not just the answer.
Convert 25°C to Kelvin Calculate TUR Unit conversions (NIST SP 811)
🎯
Exam Prep
Explore ASQ CCT Body of Knowledge topics with practice questions and concept explanations. Explorer provides foundational coverage — upgrade to unlock full CCT mock exams and readiness scoring.
CCT BoK overview Calibration concepts Measurement fundamentals
📄
Documents
Ask questions about specific metrology standards and documents in the MetLibrary — ISO 17025 clauses, VIM definitions, NIST GUM guidance, and more. Get clause-level answers grounded in the source.
ISO 17025 §6.4 VIM definition of measurand NIST GUM overview
MetLibrary

Answers from standards, not the internet.

MetTutor’s answers don’t come from a general web crawl. They come from MetLibrary — a dedicated, curated knowledge base of 950+ authoritative metrology documents, managed and version-controlled to reflect current international standards.

Every response includes a citation so you always know which standard your answer is grounded in. That’s the difference between informed guidance and a guess.

Explorer users have full access to MetLibrary citations across all four learning modes.

ISO/IEC 17025:2017
General requirements for testing and calibration laboratories
NIST GUM / TN 1297
Expression of measurement uncertainty
VIM · JCGM 200:2012
International vocabulary of metrology
JCGM GUM:2008
Guide to the expression of uncertainty in measurement
NIST SP 811
Guide for the use of the International System of Units
ASQ CCT Body of Knowledge
Certified Calibration Technician exam framework
ANSI/NCSL Z540.3
Requirements for the calibration of measuring and test equipment
ILAC G8 / P14
Guidelines on the reporting and use of measurement uncertainty
+ hundreds more across NCSLI, A2LA, OIML, and industry references
DAILY QUIZ Question 2 of 3
According to the VIM, what is the definition of “measurement uncertainty”?
The error in a measurement result
A non-negative parameter characterizing the dispersion of quantity values attributed to a measurand
The standard deviation of repeated measurements
The difference between the measured and true value
🔥 12-day streak
VIM 2.26 · JCGM 200:2012
Daily Quiz & Streak

Three questions. Every day. Free.

Consistent practice is how metrology knowledge actually sticks. Explorer’s daily quiz builds your vocabulary, sharpens your recall, and tracks your momentum with streak badges.

🗓️
3 curated questions daily
Fresh metrology topics drawn from MetLibrary
🔥
Streak tracking & badges
Build a daily learning habit and earn recognition
📝
Explained answers with citations
Every answer references the source standard
⬆️
Unlimited quizzes on paid plans
Remove the daily cap — upgrade to Student or above
Accessibility & Workflow

Learn in the way that works for you

MetTutor is designed to fit into how you actually work — in the lab, at your desk, or on the go.

🎙️ Voice Input & Read-Aloud

Ask MetTutor a question using your microphone — no typing required. Have any response read aloud, including complex uncertainty calculations and standard references. Ideal when your hands are occupied in the lab or when reviewing material while moving.

Microphone input Read-aloud per message Hands-free learning

📤 Export Any Answer

Every MetTutor response can be exported in the format that fits your workflow. Save a step-by-step problem solution to Word for your records, export a concept explanation to PDF for a team briefing, or pull data to CSV for a spreadsheet. The full export suite is included free with Explorer.

Word (.docx) Excel (.xlsx) PDF CSV TXT

Ready to go deeper?

Explorer gives you a complete foundation. When you’re ready for uncertainty calculations, ISO 17025 guidance, CCT exam prep, or team tools — a paid plan picks up right where Explorer leaves off.

  • ✓ Full GUM (JCGM 100) uncertainty calculations — from $9/mo
  • ✓ TUR calculator · ISO 17025 clauses — from $9/mo
  • ✓ 110Q CCT mock exam · spaced repetition — from $29/mo
  • ✓ NCSLI · A2LA · MSA/GR&R · decision rules — from $49/mo
  • ✓ Team seats · manager dashboard — from $199/mo
View All Plans Continue with Explorer
Cal Tech, Metrologist & Lab Manager include a 14-day free trial
Explorer FAQ

Common questions

Yes. Explorer is permanently free — there is no trial period, no expiry date, and no credit card required. All core features including the AI tutor, MetLibrary citations, four learning modes, daily quiz, voice input, read-aloud, and the full export suite are included at no cost, with no limits on how long you can use them.
MetLibrary is MetTutor’s dedicated RAG knowledge base — a curated collection of 950+ authoritative metrology documents including ISO 17025:2017, NIST GUM, VIM (JCGM 200:2012), NIST SP 811, JCGM GUM:2008, ANSI/NCSL Z540.3, ILAC guidelines, and the ASQ CCT Body of Knowledge. Explorer users receive full MetLibrary citation access across all four learning modes. Every answer MetTutor gives includes a reference to its source standard.
Explorer does not include: full GUM (JCGM 100) uncertainty calculations, the TUR calculator (ANSI/NCSL Z540.3), ISO 17025 clause-level guidance, the 110-question timed CCT mock exam, CCT readiness scoring, spaced repetition (SM-2), ILAC compliance guidance, NCSLI Recommended Practices, A2LA guidance, MSA/GR&R, JCGM 106 decision rules, or team and manager features. These are available on paid plans starting at $9/month. Explorer’s daily quiz is limited to 3 questions per day — paid plans remove this cap.
You can explore MetTutor before signing up, but creating a free account unlocks the full Explorer experience — including streak tracking, Concept of the Day, saved quiz history, and your export history. Registration requires only a name and email address, no payment information.
Explorer covers metrology fundamentals, measurement concepts, VIM vocabulary, NIST SI units, unit conversions, the history of metrology, and the Metrology Skills Matrix — all valuable for day-to-day reference. For working technicians who need uncertainty budget calculations, TUR analysis, ILAC compliance guidance, or CCT exam preparation, the Cal Tech plan ($29/month, 14-day free trial) provides the professional toolkit built specifically for calibration work.
Yes — you can upgrade at any time from your Account page. Upgrades take effect immediately. All paid plans except Student include a 14-day free trial with no credit card required. Your Explorer account, quiz history, and Concept of the Day progress carry forward when you upgrade.