How to Change Aspect Ratio in iMovie

If you're an iPhone, iPad, or Mac user, Apple's iMovie is a free video editing tool worth mastering. One important setting to understand is aspect ratio, which determines how your video looks across different platforms. For instance, YouTube favors the 16:9 widescreen format, whereas TikTok and Instagram Stories work best with a 9:16 aspect ratio. 

The challenge is that custom formats like 1:1 or 4:5 are not supported by iMovie. In this guide, you'll learn how to change aspect ratio in iMovie on Mac and iPhone, and share quick fixes to make sure your videos look great on any platform.

Part 1：What Aspect Ratios Does iMovie Support?

The aspect ratio of a video is simply the proportion between its width and height. iMovie mainly supports two formats by default: 16:9 (landscape) and 9:16 (vertical). On both Mac and iPhone, if a video is shot horizontally, iMovie automatically sets it to 16:9. If the video is recorded vertically on an iPhone, it defaults to 9:16.

The limitation here is that iMovie does not provide custom formats such as 1:1 (square), 4:5 (Instagram feed), or 2.35:1 (cinematic). Therefore, when you import a video in a different ratio, iMovie will either crop the video to fit (cutting off parts of it) or add black bars to the sides or to the top and bottom.

Part 2: How to Change Aspect Ratio in iMovie on Mac

Here are the steps you need to change the aspect ratio on a Mac:

Step 1: Create a new project

To begin, log in to iMovie on your Mac and then create a new project.

Step 2: Import your video

You can either drag and drop your video directly into the timeline or click Import Media to browse and select your clip. iMovie supports common formats like MP4, MOV, and AVI, so most videos can be added without conversion.

Step 3: Adjust aspect ratio

Click on the video clip in the timeline to reveal editing tools. You have two main options:

• Crop to Fill – Enlarges the video to fill the 16:9 frame, but crops out the edges.
• Fit – Keeps the entire video visible but adds black bars to maintain the original aspect ratio.

Step 4: Rotate if needed

If you want to alternate between horizontal and vertical formats, use the Rotate button, that is, if your video is not in the proper orientation.

Step 5: Export your video

When you're ready, click File > Share > File to export your project.

You can customize:

• Resolution: 720p, 1080p, or 4K, depending on the quality you want.
• Format: MP4 (recommended for smaller file size and easy sharing) or MOV (higher quality but larger file).
• Quality: Low, Medium, High, or Best (ProRes).

Once you've finished editing and set the right aspect ratio, you can easily upload your video directly to platforms like YouTube, Instagram, or TikTok, ensuring it looks professional and fits perfectly on any screen.

Part 3: How to Change Aspect Ratio in iMovie on iPhone

Here are the steps to adjust the aspect ratio of your video on an iPhone:

Step 1: Create a new project

Open iMovie, tap the + sign, and select Movie to start a new project.

Step 2: Import your video

Browse your device storage, tap the video you want to edit, then tap Create Movie. The clip will be added to your timeline.

Step 3: Adjust aspect ratio

Tap the video in the timeline to bring up the editing tools. Then, tap the magnifying glass icon in the preview window to enable the Pinch to Zoom tool.

• Pinch outwards to zoom in and fill the 16:9 frame (this may crop the edges).
• Pinch inwards to show the full video inside the frame (which may leave black borders).

This way, you manually control how the video fits, since iMovie for iPhone doesn't have explicit Crop to Fill or Fit buttons like the Mac version.

Step 4: Export the video

When you're done, tap Done > Share > Save Video.

• Vertical clips will export in 9:16, perfect for TikTok, Instagram Reels, and YouTube Shorts.
• Horizontal clips will export in 16:9, ideal for YouTube or widescreen playback.

Please note that iMovie doesn't support custom ratios like 1:1 or 4:5, so you'll need to export and resize in another app if you want the above formats.

Part 4: FAQs About How to Change Aspect Ratio in iMovie

1. How do I resize a video in iMovie?

To resize a video in iMovie, open the Crop settings and choose either Crop to Fill or Fit. This allows you to control the aspect ratio and make sure the video fits the frame the way you want.

2. Does iMovie support a 9:16 ratio?

Yes. iMovie supports the 9:16 vertical aspect ratio, but only if the video was originally recorded in portrait mode (such as on an iPhone).

3. Why does iMovie change screen size?

By default, iMovie automatically adjusts the screen size and aspect ratio of your clips to either 16:9 (landscape) or 9:16 (portrait), depending on how the video was recorded.

4. How do I get rid of black bars in iMovie?

Select Crop to Fill in the crop settings. This option resizes the video to fill the frame completely, removing the black bars.

5. How do I make iMovie full screen on iPhone?

When previewing your project, rotate your iPhone to landscape mode. iMovie will automatically play the video in full screen.

Conclusion

Although iMovie is one of the most popular video editing programs for beginners, its aspect ratio options are somewhat limited. By default, it only supports 16:9 for landscape videos and 9:16 for vertical videos. Custom ratios like 1:1 for square videos or 4:5 for Instagram feed require exporting your project and using another app.

Alternatively, you could use a device like the OBSBOT Tail 2 to shoot directly in the format you need. Knowing how to change aspect ratio in iMovie helps ensure your videos work on any platform, saving time and improving your editing workflow.