GD&T Quest

Learn geometric tolerancing the fun way — then prove it. Unlimited retries, always.
⭐ Level 1
✨ XP 0
🔥 Streak 0
🏅 Best —
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Player
Start here — your path through GD&T
Nine short steps. Each one is a few minutes. Steps tick themselves off as you go.
① Before you start — three things every drawing assumes
Units
Every number in this trainer is in millimetres. A tolerance of 0.05 is five hundredths of a millimetre — about the thickness of a sheet of paper.
Plain numbers have ±
A size like ⌀8.4–8.6 or 12 ±0.1 says how big a feature may be. Measure it with calipers or a micrometer: inside the limits = good.
Boxed numbers are exact
A number in a box, like 70, is a basic dimension: the perfect, theoretical distance, with no ± of its own. The allowed error for that feature lives in its feature control frame instead.
A feature control frame
A row of boxes read left to right: what is controlled (symbol), how much (tolerance), measured from what (datum letters A, B, C). Build your own in the Frame Decoder.

② The 14 geometric characteristics, grouped by family. Read the five families first, then tap any card. Each card answers the same nine questions, so you always know where to look.

How to read the families
🟦 Form
Is the feature itself the right shape? Needs no datum — it floats free.
🟩 Orientation
Is it at the right angle to a datum? Needs a datum.
🟨 Location
Is it in the right place? Needs a datum.
🟧 Runout
How much does it wobble when spun? Needs a datum.
🟪 Profile
The shape of any surface — the catch-all. Datum optional.
Rule of thumb: form compares a feature to itself. Orientation, location and runout compare it to a datum.
④ Tell them apart — the five pairs everyone mixes up

Each pair below looks alike on a drawing. The table shows the one clue on the drawing that separates them, and a real part that passes one and fails the other.

⑤ MMC and bonus tolerance — a worked example with numbers
⑧ A complete worked drawing — read it like an inspector
📖 Glossary — the words people trip over

“Sounds like” is what most people assume. “Actually means” is what the standard means.

A feature control frame is the sentence of GD&T. Build one below and it reads itself back to you in plain English.

Characteristic
Diameter symbol?
Tolerance value
Material modifier
Datums

What is a datum, really? It is simply the reference you measure FROM — but it doesn't have to be a flat face. It can be a round bore, a slot, a ball, or a pair of holes, and each type takes away a different number of the 6 ways a part can move. Pick one below and watch. Then scroll down for the classic 3-2-1 rule.

What kind of feature is your PRIMARY datum (A)?
…
🧱 The classic 3-2-1 rule (flat-face datums)

A free part in space has 6 ways to move: slide up/down, slide left/right, slide in/out, and tilt three ways. A datum takes those away one at a time. Toggle the constraints and watch the degrees drop to zero.

0 of 6 degrees locked — part is FLOATING free

The part starts loose. It drops onto datum A (3 points: one slide and two tilts gone), is pushed against B (2 points: a slide and the spin gone), then against C (1 point: the last slide gone).

Primary plane (Datum A)3 points under the part — stops 3 ways of moving
Secondary plane (Datum B)2 points on the side — stops 2 more
Tertiary plane (Datum C)1 point on the end — stops the last one
Why 3, then 2, then 1?
• The primary face touches on 3 points → kills 3 (up/down slide + 2 tilts)
• The secondary face touches on 2 points → kills 2 more (a slide + the spin)
• The tertiary face touches on 1 point → kills the last 1 (the remaining slide)
That is why a drawing writes A | B | C in that exact order — the order is the order you seat the part.

Real engineering reference diagrams — tap any image to zoom. These diagrams appear in picture-round quiz questions.

Your progress on this device. Nothing here is sent anywhere unless you log in and finish a quiz.

Learning path
Quizzes
How sure are you on each characteristic?

Achievements
What this is

GD&T Quest teaches geometric dimensioning and tolerancing — the symbols on engineering drawings that say how flat, round, square or well-placed a feature must be. It covers the 14 geometric characteristics of ASME Y14.5-2018, and points out where ISO 1101 differs (concentricity and symmetry, removed from ASME in 2018).

It is an independent training project. It is not affiliated with, or endorsed by, ASME, ISO or any employer.

How to use it
  1. Open Learn and follow the nine-step path.
  2. Build frames in the Frame Decoder and play with Datums.
  3. Practise in Quiz — untimed, unlimited, every answer explained.
  4. When ready, take the Full Assessment for a certificate.

Press / anywhere to search. Everything works with a keyboard.

Meet Shim, your guide

Shim is a hex-nut maintenance drone. It watches what is on your screen and offers one short, plain explanation of it — never during a quiz, and never over a button.

Turn Shim on or off with the Guide switch at the top. In its bubble: Quiet mode (only speaks when tapped), Snooze for this visit, and Read aloud (off unless you press it).

Offline & install

On a secure (https) address you can install GD&T Quest like an app, and the learning pages, diagrams and practice quizzes keep working without a connection. Accounts, the assessment and certificates need the server.

What is stored

On this device: your progress, XP and settings. On the server, only if you create an account: your name, email, a salted password hash, quiz scores, assessment results and certificates.

Pass the Full Assessment (30 questions, 80%) and you get a certificate in your name, with an ID anyone can check on the verification page.

How it works
  1. Log in, and check the name below is the one you want printed.
  2. Open Take the Quiz and start the Full Assessment. Two questions on each of the 14 characteristics.
  3. Score 24 of 30 or more. It is marked on the server, then your certificate appears here — print it, save it as PDF, or share its ID.

Not this time? Every answer is explained at the end, with a link to the card that teaches it. Retakes are unlimited.

Your certificates
Log in to see your certificates.

Get a question wrong? No drama — you get the answer, the why, a link to the card that teaches it, and unlimited retries. Nothing here is timed.

Level for the Mixed Quiz
🎯

Mixed Quiz — 10 questions

Symbols, frames, datums and real-world judgement, shuffled fresh every run.

🖼

Picture Round — 10 questions

Read real engineering tolerance-zone diagrams and answer. The hardest round.

🔤

Symbol Drill

Rapid-fire through all 14 symbols, one at a time. Perfect for learning the glyphs.

🎓

Full Assessment — 30 questions

Two questions on every one of the 14 characteristics, all three levels. Pass mark 80% (24 of 30). Marked on the server; passing issues a certificate in your name. Answers are revealed, with explanations, at the end.