user1809: It's possible to change the dimensions of a Shape in AE under Transform > Scale.
But what if I want pixel values? Is it possible to change the exact pixel dimensions of a Shape w/o resorting to expressions?

user24714: If you are using Adobe Afer Effects CC 2019, you can do the following to edit the Shape dimensions in pixels.

Right click on the Shaper layer. In the menu that shows up, find the option "Transform". Highlight it to reveal the "Scale..." option. Click on it. Check the screenshot below.



Doing so will launch a small dialog asking you to select the "Units" and will also give you the provision to enter the dimensions in digits. Enter the digits as you like. I entered 1920 & 1080. Then click on Ok. Check the screen below.


That's it. Enjoy!!!

user11523: On the layer "Scale" value:
Right Click => Edit Value...
There you will see dialogue box: 

How you can see, you can change it there.

1809: <p>It's possible to change the dimensions of a Shape in AE under Transform > Scale.</p>

<p>But what if I want pixel values? Is it possible to change the exact pixel dimensions of a Shape w/o resorting to expressions?</p>
 24714: <p>If you are using Adobe Afer Effects CC 2019, you can do the following to edit the Shape dimensions in pixels.</p>

<ol>
<li>Right click on the Shaper layer. In the menu that shows up, find the option "Transform". Highlight it to reveal the "Scale..." option. Click on it. Check the screenshot below.</li>
</ol>

<p><a href="https://i.stack.imgur.com/vAScQ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vAScQ.jpg" alt="Right Click options on a Shape Layer"></a></p>

<ol start="2">
<li>Doing so will launch a small dialog asking you to select the "Units" and will also give you the provision to enter the dimensions in digits. Enter the digits as you like. I entered 1920 &amp; 1080. Then click on Ok. Check the screen below.</li>
</ol>

<p><a href="https://i.stack.imgur.com/pi7XZ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pi7XZ.jpg" alt="Small dialog to edit Shape Dimensions in Pixels"></a></p>

<p>That's it. <strong>Enjoy!!!</strong></p>
 11523: <p>On the layer "Scale" value:
Right Click => <kbd>Edit Value...</kbd></p>

<p>There you will see dialogue box: </p>

<p><a href="https://i.stack.imgur.com/YUpKH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YUpKH.png" alt="enter image description here"></a></p>

<p>How you can see, you can change it there.</p>
