4.MD.6: Measure and Draw Angles with a Protractor
Also written as 4.MD.C.6 and CCSS.MATH.CONTENT.4.MD.C.6 · Cluster: Geometric measurement: understand concepts of angle and measure angles.
The Official Wording
Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.
Common Core State Standards, Grade 4, Measurement & Data · Read it at the source · Checked October 14, 2026
What 4.MD.6 Means in Plain English
Fourth graders line up a protractor’s center on the vertex and its zero line on one ray, then read where the other ray crosses the scale, like 65°. They also work in reverse, drawing a 140° angle from a single ray and a dot.
The hard part is choosing between the two scales, so students estimate first: is the angle smaller or larger than a right angle? Measured angles feed the angle equations of 4.MD.7, and in 7th grade students draw triangles from given angles (7.G.2).
4.MD.6 I Can Statements
- I can line up a protractor on the vertex and one ray.
- I can read an angle in whole degrees from the right scale.
- I can draw an angle of a given size, like 140°.
4.MD.6 Worked Example
Every ray crosses a protractor at two numbers, and this example shows how students pick the right one.
Ana lines up a protractor on an angle. The bottom ray runs through 0 on the inner scale. The other ray crosses the protractor where the scales read 50 and 130. What does the angle measure?
- Estimate before reading anything. Hold a square corner, like the corner of an index card, against the angle. The angle opens wider than the card.wider than a right angle, so more than 90°
- Check the setup: the center mark sits exactly on the vertex, and the zero line runs along the bottom ray.center on the vertex, 0 on one ray
- Use the scale that reads 0 on the starting ray. Here that is the inner scale, so follow it up from 0 to where the other ray crosses.inner scale: 0, 30, 60, 90, 120, then 130 at the ray
- The other ray crosses at 130 on the inner scale. The 50 belongs to the outer scale, which starts at 0 on the opposite side.angle = 130°
Check it: 130° is more than 90°, which matches the estimate. And 130 + 50 = 180: the two numbers under a ray always add to a straight angle, which is why the wrong one is so tempting.
Common Mistakes with 4.MD.6
Reading the wrong scale
An obtuse angle recorded as 50° instead of 130°
Try this: Estimate first with a square corner: smaller or bigger than 90°? Then follow the scale that reads 0 on the starting ray.
Lining up the edge, not the center
The protractor’s bottom edge set on the vertex, so every reading is off by a few degrees
Try this: Mark the vertex with a dot and put the protractor’s small center hole or cross on it before anything else.
Rays too short to reach the scale
A short ray that stops before the numbers, so the student guesses
Try this: Extend both rays with a ruler until they pass the protractor’s edge. A ray goes on forever, so lengthening it changes nothing.
Where 4.MD.6 Fits
Practice 4.MD.6
Quick Check
- A protractor’s zero line is on one ray, and the other ray crosses at 35 and 145. The angle is acute. What does it measure?
- How can you sketch a 45° angle without a protractor?
- Tomas reads 120° for an angle that is smaller than a square corner. What went wrong, and what is the angle?