Pixels and crop are different.
Resize changes pixel dimensions. Crop changes which part of the image survives. Changing aspect ratio often means doing one, the other, or adding empty space.
Presentation & Layout
Slide Pixel Size Calculator.
Calculate pixel dimensions for common slide ratios.
1 Enter2 Adjust3 Use result
Input
Answer
16:9
1920 × 1080
Use 1920×1080 as a strong default for 16:9 screen presentations.
Useful to know
Four things worth knowing.
It cannot invent the frame.
A new shape cannot reveal content outside the original frame, and enlarging dimensions does not create genuine captured detail.
Check the edges.
View the slide full-screen. Editing view can hide how crowded a layout feels when presented.
Size for the destination.
Pick the final destination first. A profile photo, print, story and website hero all want different shapes for a reason.