How to Manually Adjust Aspect Ratio of Videos in iMovie Editor

As a video editor using iMovie, you may often need to adjust the aspect ratio of your video projects to fit different sharing platforms. Aspect ratio refers to the proportional relationship between the width and height of an image or video frame. Some common aspect ratios used today include:

  • 16:9 – The standard widescreen aspect ratio used for HD TVs and computer monitors. Also commonly used for YouTube, Vimeo etc.
  • 4:3 – The standard fullscreen aspect ratio used by old CRT TV sets.
  • 1:1 – A square aspect ratio popularly used for social media profile pictures and thumbnails.
  • 9:16 – A tall, portrait-style aspect ratio used for social media stories and TikTok videos.

Why Aspect Ratio Matters

The aspect ratio you choose for a video project depends on:

  • The aspect ratio the video was originally recorded in
  • The platform you intend to publish the video on

For example, if you recorded a video vertically on your phone for TikTok, it would have a 9:16 aspect ratio. If you want to repurpose that same video for YouTube, you would need to adjust the aspect ratio to 16:9.

Similarly, horizontal videos shot for YouTube at 16:9 would need to be adjusted to 1:1 or 9:16 to work for Instagram or TikTok without black bars or cropping.

Adjusting aspect ratio properly before exporting your edited video ensures that your final video looks as intended without any unwanted cropping or black bars when viewed on different platforms.

Manually Changing Aspect Ratio in iMovie

Unfortunately iMovie does not have preset options to change aspect ratio to formats like 1:1, 9:16 etc. The only way is to manually crop and adjust the video frame.

Here are the steps to change aspect ratio in iMovie:

On Mac

  1. Import the video clip you want to edit into an iMovie Project
  2. Click on the Crop icon in the top toolbar
  3. Manually adjust the crop area handles to achieve the desired aspect ratio
  4. Click the blue Done checkmark to apply the crop

On iPhone/iPad

  1. Open the video clip in the iMovie timeline
  2. Tap the magnifying glass icon in the top right corner
  3. Use two-finger pinch and zoom gestures on the video clip to manually adjust the framing
  4. Tap Done to apply the crop

Tips for Adjusting Aspect Ratio

  • Pay attention to important areas while cropping manually. Avoid chopping off heads, faces or important action.
  • Use guides like gridlines while adjusting framing to get accurate dimensions.
  • For 9:16 vertical, rotate phone before recording for best quality instead of cropping horizontal video.
  • Use third party editing apps instead of iMovie if you want more fine-tuned control and preset ratios.

Common Aspect Ratios Used Today


The most common widescreen aspect ratio used for HD video, YouTube etc. Widescreen computer monitors and TVs also adopt this.


Earlier TV sets used the 4:3 aspect ratio as standard before widescreen formats became popular. Some digital cameras also still use this.


A square aspect ratio popularized by Instagram and used extensively across social media for profile pictures and thumbnails.


The tall, portrait-oriented aspect ratio used prominently by TikTok and social media stories. Also used sometimes for phone photography.


An ultra-widescreen cinematic aspect ratio used for many Hollywood blockbuster movies.

Advanced Aspect Ratio Customization

While iMovie only allows manually cropping to adjust aspect ratio, advanced video editing software like Final Cut Pro and Adobe Premiere Pro provide more fine-tuned control.

Some ways they allow customizing aspect ratios include:

  • Manually entering precise dimension values
  • Overlaying guides, grids and safe area overlays
  • Using pixel aspect ratios for anamorphic formats
  • Adding pillarboxes and letterboxes
  • Using masks along with keyframes for animation

These tools help professional editors tailor the framing and delivery requirements needed for any video project with the highest precision.


Adjusting aspect ratio in iMovie can be challenging with only manual crop as an option, but it gets the job done for most basic needs. Having an understanding of common aspect ratios and intended publishing platforms makes this easier. For professional projects or more advanced editing, third party software like Final Cut Pro would be a better option.

I hope this guide gives you a good overview of working with aspect ratios in iMovie! Let me know if you have any other questions.