To adjust a layer’s height or width, you can drag any of its edges. To adjust both the height and width at once, you can use the corner handles.
You can resize a layer by clicking and dragging anywhere on the object
Holding ⇧ will resize the layer proportionately, keeping its height and width at the same ratio.
Holding ⌥ will resize the layer from its center, rather than the edge you’re dragging from.
Note: resizing will be affected by any Resizing constraints applied.
Resizing layers in the Inspector
You can also resize a layer by selecting it and typing new dimensions in the Inspector. As you type, you’ll be able to preview how it will look. Once you are happy, click ⏎ to apply your changes.
How to resize layers using the Inspector of the Mac app (v94 October 2022).
By default, this will resize layers from their top-left corners, but you can change this using the following keyboard operators:
| l | Scale from the left (default) |
| r | Scale from the right |
| t | Scale from the top (default) |
| b | Scale from the bottom |
| c / m | Scale from the center/middle |
You can use the operators w,h,x, andy as stand-ins for the width, height, X, and Y of the selected element. For example, if you set a rectangle’s height tow it will turn it into a square.
How to use the width operator in the Inspector of the Mac app (v91 August 2022).
The Inspector also lets you use math to resize or move layers with the following:
| + | Add (e.g. 50+10r) |
| - | Subtract (e.g. 45-5) |
| * | Multiply (e.g. 128*2) |
| / | Divide (e.g. 960/2) |
Resizing controls in the Inspector of the Mac app (v91 August 2022).
You can also use percentages to change the height or width of layers relative to its group or Artboard. For example, setting a layer’s height to 10% in a 960 pixel-wide Artboard will change its width to 96px.
Finally, if you’re editing the corner radius of a rounded rectangle, you can use ; to specify a different value for each corner (e.g. 30;40;20;30).
You can click the lock icon 
that’s between the width and the height values or use the shortcut ⌥⌘L to make sure the layer resizes proportionately.
Resizing layers with keyboard shortcuts
For precise adjustments, you can select layers and resize them using the following keyboard shortcuts:
| ⌘→ | Increase width by 1px |
| ⌘← | Decrease width by 1px |
| ⌘⇧→ | Increase width by 10px |
| ⌘⇧← | Decrease width by 10px |
You can set your own increment values for these shortcuts using the Nudging options in the Canvas tab of the Preferences window.