How to draw an open mouth: lips parted and jaw dropped

A quick open mouth is often drawn as the closed mouth with a dark oval cut into it, so the lips get thinner as the hole gets bigger. On the drawings measured here, the lips stay at least as thick as they were and the opening is added between them. It comes in two kinds. In the smaller one the upper lip lifts off the teeth and the chin moves half an iris width at most. In the larger one the jaw comes down and takes the lower lip with it. This guide compares one study head drawn at rest with two open mouths, so you can see how far each part moves. It covers a realistic open mouth from the front, not cartoon mouths or the side view.

The unit is the width of one iris, measured straight across. The three drawings are at slightly different sizes, so each is measured with its own iris.

The lips don't get thinner

Measure each lip on the center line of the face. Take the upper lip from its top edge down to the line where the lips meet, or to the top of the opening once the mouth is open. Take the lower lip from that line, or the bottom of the opening, down to the middle of the dark stroke under it.

At rest the upper lip is about two thirds of an iris width thick and the lower lip about one iris width. In both open mouths the upper lip is about three quarters of an iris width at the middle and the lower lip still about one iris width. A little to either side of the center the lower lip still measures about one iris width, and the upper lip comes out fuller in the large opening, about five sixths of an iris width against about two thirds at rest.

So when you open a mouth, keep both lips at least as thick as they were, or the upper lip a little fuller, and add the opening between them. The lower lip stays the thicker of the two.

A small opening: the lips part

In the first open mouth the lips part by a little under one iris width at the middle. The opening is long and low, about five times wider than it is tall, and the mouth is about as wide as at rest.

The upper lip comes up toward the nose: the gap from the base of the nose to the top of the upper lip shrinks to about two thirds of its resting height. How much the lower lip moves depends on what you measure from. Measured down from the center of the iris, the bottom of the lower lip and the chin sit where they were at rest. Measured down from the base of the nose, both sit a little under half an iris width lower. The two drawings place the nose differently, so we can't tell which is right; either way the jaw moves far less than in the large opening.

The teeth fill the opening. The upper teeth show about half an iris width and the lower teeth about a third, and the line where they meet sits a little below the middle of the opening. The corners stay where they were at rest, about half an iris width inside a line dropped from the center of each iris, just below the middle of the opening.

A large opening: the jaw drops

In the second open mouth the opening is about two and a quarter iris widths tall at the middle, measured between the inner edges of the lips. It's still wider than it is tall, by about one and a half times. The chin comes down one and a half to two iris widths: about one and a half measured from the iris centers, about two measured from the base of the nose. The whole lower face gets longer, and the lower lip goes down with it.

The mouth gets narrower as it opens: about a fifth narrower than at rest. Its corners land about one iris width inside the lines dropped from the iris centers, and a little above the middle of the opening. The gap from the nose to the upper lip gets about a sixth shorter.

Inside, a strip about a quarter of an iris width tall shows under the upper lip, the edge of the upper teeth. Below that the drawing uses only a few light lines.

Inside the mouth

Neither drawing fills the opening with dark tone. In the small opening the teeth are left almost white, with darker tone only toward the corners. In the large one the opening is mostly white with a few light lines.

How to draw an open mouth, step by step

1. Draw the mouth at rest. Place the base of the nose, the top of the upper lip, the lip line, the bottom of the lower lip and the chin, and measure one iris width.
2. Choose the kind of opening. For a small one the upper lip does most of the moving; for a large one the chin comes down.
3. For a small opening, keep the lower lip where it was or lower it by up to half an iris width, and raise the upper lip at its own thickness until the lips part by a little under one iris width at the middle.
4. For a large opening, lower the chin by one and a half to two iris widths, bring the lower lip down with it, and open the lips to about two and a quarter iris widths at the middle. Bring the corners in so the mouth is about a fifth narrower.
5. Redraw each lip at least as thick as before, about two thirds to three quarters of an iris width for the upper lip and about one for the lower.
6. Add the teeth lightly: the upper teeth just under the upper lip, and in a small opening the line where the teeth meet a little below the middle.
7. Match the tone of your reference inside. These drawings leave the opening mostly light; darken the corners and the deepest part only where your reference shows darker tone.

Common mistakes

• Thinning the lips as the mouth opens. On these drawings neither lip gets thinner.
• Opening a large mouth without moving the chin. Here the chin comes down one and a half to two iris widths.
• Leaving the upper lip where it was in a small opening. Here it comes up toward the nose.
• Keeping a wide-open mouth at its resting width. It narrows by about a fifth.
• Filling the opening with black. Both drawings leave it mostly white.

What this does and does not cover

These are three drawings of one study head, made as separate models: at rest, lips parted in an angry face and jaw dropped in a surprised face. With one drawing of each, we can't separate what the expression changes from what simply differs between drawings; take these numbers as a description of this set. The two open drawings also place the nose about half an iris width closer to the eyes than the resting one, so heights measured from the eyes and from the nose disagree by about that much; where it matters we give both. A smiling, speaking or laughing open mouth isn't drawn here, and we measured only the front view.

A short exercise

Draw a closed mouth from the front with the eyes, the nose base and the chin, then copy it twice. Turn one copy into a small opening and the other into a large one, checking each lip's thickness against the iris. Compare the lips and the openings with the figure. For the chin, line your three drawings up on the eyes: the small opening should move the chin half an iris width at most, and the large one should be longer in the face and narrower at the mouth. For the parts themselves, see how to draw lips from the front, the mouth and lips at different angles and how to draw a jawline. The two faces these mouths come from are in how to draw an angry face and how to draw a surprised face; a smile keeps the lips closed.

The rest, anger and surprise plates, with the construction lines drawn over them, are in How to Draw the Head, the 43-page book included with Volume 1 and Volume 2. The rest of the head, angle by angle, is in how to draw the head at any angle.