📐
Measured AngleAcute
45.00°(Outer: 135.00°)
Ready: Drag angle arm handle or vertex to measure. Output updates continuously.
Gamified Angle Quiz
Protractor Angle Practice
Test your angle estimation and protractor reading skills with interactive quizzes and instant scoring.
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STEP 1
Move center circle to angle corner, then rotate arm to match edge.
Angle45.0°
Angle45.0°
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Comprehensive Geometry & Engineering Handbook
Online Free Protractor & Screen Ruler · onlinefreeprotractor.com
✓ 100% Client-Side Private · Local RAM
⠿📏 Screen Ruler
Dist: 0.00 cmDrag Blue Center to vertex · Drag Arm Handle to rotate
⠿💳 Card
85.60 × 53.98 mmScale: 100 px = 10.0 cm
Bubble Level
MEASURED ANGLE OUTPUT
45.00°
ACUTE
Outer: 135.00° · 0.7854 rad
Supplementary
135.00°
Complementary
45.00°
Trigonometric Ratios
sin: 0.7071 · cos: 0.7071
Device Calibration
113.0 PPI · 1:1 Scale
RECORDED ANGLE PINS
| # | Angle (Deg) | Radians | Type |
|---|
Primary ScaleInner Scale
45.00°Acute
Outer Scale135.00°
Angle Relationships
Supplementary (180°-θ):135.00°
Complementary (90°-θ):45.00°
Reflex (360°-θ):315.00°
Trigonometric Values
sin(θ):0.7071
cos(θ):0.7071
tan(θ) (Slope):1.0000
Circle Geometry
Arm Radius:200 px
Arc Length:157.08 px
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Recorded Measurements0 Pins
| # | Label | Degrees | Radians | Class | Action |
|---|---|---|---|---|---|
| No pinned angles yet. Click canvas to place ray pins or click "+ Save Reading". | |||||
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Interactive Training
How to Practice & Master Reading Angles
Follow these 3 simple training steps to build geometric intuition and ace your geometry tests.
01
Generate Random Angles
Click New Angle to generate a challenge or pick a real-world scenario (such as a 26.5° roof pitch or 45.0° miter saw angle).
Acute, Obtuse & Reflex Challenges
02
Read Degrees or Construct Target
In Measure Mode, type your degree estimate into the box. In Construct Mode, drag the interactive arm to create the requested angle.
Interactive Drag & Type
03
Instant Feedback & Scoring
Receive instant scoring, error difference analysis, and angle classification to rapidly improve your geometric skills.
Real-Time Score Tracker
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Quiz & Practice FAQs
Protractor Practice FAQs
Common questions about practice modes, grading tolerance, kids math practice, and classroom usage.
What is the difference between Measure Mode and Construct Mode?↓
Measure Mode: A random angle is drawn on screen, and you must read the protractor markings and type your degree value into the guess box. Construct Mode: The app asks you to construct a specific target angle (e.g. "Create 135°"), and you drag the protractor arm to hit the target degree.
What is the tolerance for correct answers?↓
The practice quiz accepts answers within a standard educational tolerance of ±2 degrees as correct to accommodate hand drag precision and visual alignment nuances on mobile touchscreens.
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Can teachers use this in math and geometry classrooms?↓
Yes! This tool is 100% free with no login or student account requirements. It works seamlessly on interactive whiteboards, smart TVs, Chromebooks, iPads, and PCs.
What real-world engineering scenarios are included?↓
You can test practical angles found in everyday engineering: standard roof pitch (26.5° / 6:12 pitch), woodworking 45° miter cuts, industrial 118° drill bit tip angles, 120° hex bolt facets, and 35° optimal solar panel tilt angles.