How to draw an angle in AutoCAD, and where zero degrees points

Learning to draw an angle in AutoCAD sounds too simple to stop and study. Then a 30-degree roof pitch, a 45-degree wall or a line square to a sloping edge turns up, everyone does it a different way, and the results disagree.

This article gathers the four methods in one place, together with the groundwork almost no guide mentions: which direction counts as zero degrees, and which way the numbers grow. Each method below is a different way to draw an angle in AutoCAD, and none of them is wrong — they simply fit different moments in the drawing. For the whole drafting and documentation workflow, see the AutoCAD for Construction course.

Where zero degrees points, and which way angles count

Every angle you type is measured from a datum. Not knowing that datum is how a typed 45 ends up pointing somewhere else entirely.

Type UNITS and click Direction to reach the dialog above. The four cardinal directions carry their values: East is 0, North is 90, West is 180, South is 270. East is preselected, so zero degrees points to the right.

Two variables govern this, and their names are worth knowing for when an unfamiliar drawing arrives.

The angle override in AutoCAD, typed with a less-than sign

This is the quickest method and the least known. While a command is asking for the next point, type < followed by the angle, for instance <30, and press Enter.

```

Command: line

Specify first point: pick the start point

Specify next point or [Undo]: <30

Angle Override: 30

Specify next point or [Undo]: drag, then type the length

```

Its proper name is the angle override. The cursor locks to that angle and only the length stays free, so one more number finishes the line.

The About Specifying Distances, Lengths, and Angles page states a precedence rule no guide repeats. The angle you type "will lock the cursor, overriding Grid Snap, Ortho mode, and PolarSnap", yet "coordinates and object snaps take precedence over an angle override".

So it beats snap, ortho and polar. But if the cursor happens to catch an object snap, that snap wins and the locked angle is discarded. This is why people lock an angle and still watch the line come out crooked.

Polar coordinates: draw a line at an angle and give its length at once

The method above locks the angle first and takes the length afterwards. When both are known, type them together as a relative polar coordinate.

The syntax is @length<angle. So @2500<30 draws a line 2500 units long at 30 degrees above the horizontal, starting from the point you just picked.

The @ means "measured from the last point", not from the drawing origin. Drop it and the figure jumps back to 0,0. Coordinate entry is covered in full in entering coordinates in CAD.

The dynamic input tooltip carries a trap. Autodesk states that it "displays only acute angles: all angles are displayed as 180 degrees or less", so an angle of 270 degrees reads as 90, whatever ANGDIR is set to. The number in the tooltip is for looking at, not for checking your work against.

Polar tracking: snap the cursor to the angles you choose

The two methods above suit one-off lines. Drawing a run of lines at the same angle calls for setting an increment once and then simply dragging.

Press F10 to toggle it, or type DSETTINGS and open the Polar Tracking tab for the detail.

The last group is the one to remember. Drawing a chain where each leg turns 15 degrees from the previous one is trivial with Relative to last segment, and tedious without it, because you would be adding angles in your head. Almost nobody uses it, because almost nobody knows it is there.

Increment angle is the POLARANG variable, and reading it from the command line holds a surprise. The variable stores radians, not degrees: a 90-degree step reads back as 1.5708, which is half of pi. Setting it by typing POLARANG still takes degrees as usual.

Three ways to draw a 45 degree line in AutoCAD

The 45-degree case comes up often enough to deserve its own section. All three give the same geometry; they differ in what you already know.

There is a fourth route for construction geometry. The XLINE command with the Ang option draws a line of infinite length at a given angle, handy as a guide to trim away later.

That Ang option has a sub-option called Reference, which sets the angle relative to an existing line rather than to the horizontal. The XLINE page notes that this angle is measured counterclockwise from the reference line.

One more branch is worth knowing: Bisect. It draws the bisector of an angle directly — pick the vertex, pick the first side, pick the second. No construction geometry required.

How to draw a perpendicular line in AutoCAD

Perpendicular to the horizontal is easy: switch on ORTHO with F8, or type @3000<90. The awkward case is perpendicular to a sloping edge.

Do not calculate the angle for that. Use the Perpendicular object snap: run LINE, pick the start point, then hover over the sloping edge until the perpendicular symbol appears and click. AutoCAD works out the foot of the perpendicular itself.

It works the other way round too, starting from a sloping edge. Run LINE, type PER and Enter, click the edge, then pick the destination. Object snaps are covered in full in object snap in AutoCAD.

One habit is worth building early. Decide which of the four methods you are using before you start the command, rather than reaching for the mouse and correcting afterwards. Correcting a line that is nearly right takes longer than drawing it right, because the geometry it connects to has already moved.

Three different jobs often get lumped together as "angles". Drawing an angle sets a line on a slope. Chamfering cuts the corner where two lines meet, covered in the CHAMFER command. Filleting rounds that same corner, covered in the FILLET command.

Measure an angle in AutoCAD, and why it always reads acute

Measuring and dimensioning are two different jobs done by two different commands.

To read a value for yourself, type MEASUREGEOM and choose Angle. It accepts four things: an arc, a circle, two lines, or three points you pick yourself.

The MEASUREGEOM page gives two details that decide how you read the result. First, for two lines it measures "the acute angle between two selected lines" — it always returns the acute one. Meet a 120-degree corner and it reports 60, leaving you to subtract from 180.

Second, "the lines do not need to intersect". Two lines that never meet still measure, because the program extends them mentally.

To put the number on the drawing for somebody else, use DIMANGULAR, aliased DAN. That creates a real dimension with a dimension line and text, and it follows the drawing's dimension style as described in dimensions in CAD.

A command called ANG circulates online as the way to measure angles. AutoCAD has no such command. Typing it returns an unknown command message. It is most likely a confusion with the Ang option inside XLINE, and that option draws rather than measures.

Frequently asked questions

Why does a line typed at 45 point somewhere else entirely?

Check ANGBASE and ANGDIR. A drawing from outside may have moved the angle datum or reversed the direction. Type UNITS and click Direction to see.

I locked the angle with a less-than sign, so why is the line still crooked?

Object snaps and coordinates outrank a locked angle. If the cursor caught a snap on the geometry, that snap won. Turn off the running snaps and draw it again.

Why does the measurement read 60 when the corner is plainly obtuse?

MEASUREGEOM always returns the acute angle between two lines. Subtract from 180 for the obtuse one. To put the correct number on the drawing, use DIMANGULAR.

How do I work out the angle for a line square to a sloping edge?

You do not. Use the Perpendicular object snap and let AutoCAD find the foot of the perpendicular.

Why does the dynamic tooltip show 90 while I draw a 270-degree angle?

The tooltip only ever shows acute angles, folding everything to 180 degrees or less. It is a display convention, not the value you entered.