Edit video size on your phone: aspect ratio, resolution and file size

When people say they want to edit video size, they can mean one of three things. The first is the shape of the frame (aspect ratio). You change it by cropping: in Photos on iPhone, or in Google Photos on Android. The second is the resolution, the number of pixels. You change it when you save or export, for example with Size and format in Samsung’s Gallery or the resolution setting next to the export button in an editor such as CapCut. The third is the file size in megabytes. That follows from the resolution, the frame rate, the format and the length, so you make a file smaller by reducing one of those. The rest of this guide covers each one step by step.

Three kinds of size, and which one you need

Work out which one you need before you open an app. If you crop when you only needed a smaller file, you lose part of the picture for no reason.

You want to…	What changes	On iPhone	On Android
Make a horizontal clip vertical or square	Aspect ratio	Photos: Edit, Crop	Google Photos: Edit, Crop
Make the picture fewer pixels (4K to 1080p)	Resolution	An editor with an export resolution setting	Samsung Gallery: Size and format, or an editor
Make the file small enough to send or upload	File size	Lower resolution, HEVC format, shorter clip	Lower resolution, HEVC, shorter clip

Change the shape: crop to 9:16, square or 16:9

Crop a video on iPhone

1. Open the video in Photos and tap Edit.
2. Go to the crop tool.
3. To crop freely, drag the corners or edges of the grid.
4. To use a fixed shape, tap the aspect ratio button and pick a preset. The list includes Freeform, Square, 9:16, 4:5 and others (iDownloadBlog).
5. Tap Done. If you change your mind while editing, Reset undoes the crop (iDownloadBlog).

Apple has moved some of the Photos controls around between iOS versions, so the buttons on your phone may look different. The steps stay the same.

Crop a video on Android

1. Open the video in Google Photos and tap Edit.
2. Tap Crop.
3. For a fixed shape such as a square, tap Aspect ratio and choose one.
4. Tap Save to keep a copy with your edits (Google).

Video cropping in Google Photos needs at least 1 GB of RAM and Android 6.0 or later. On non-Pixel phones running Android 9, video editing is not supported at all (Google).

What cropping costs you

When you crop, you throw pixels away. Cropping a horizontal 1920 × 1080 clip to 9:16 keeps a strip about 608 pixels wide and 1080 tall. That is less than a third of the frame, and you have to keep your face inside that strip. If you know the video is for Reels or Shorts, hold the phone upright while you record and you won’t need to crop at all.

It helps to know what each platform takes. Instagram accepts Reels with an aspect ratio between 1.91:1 and 9:16. It asks for at least 30 frames per second and a resolution of at least 720 pixels (Instagram). YouTube describes Shorts as vertical videos up to three minutes long (YouTube). For the rest of the posting workflow, see our guides on editing Instagram Reels and editing YouTube Shorts.

Change the resolution

On a Samsung Galaxy

1. Open the video in Gallery and tap Edit.
2. Tap More options, then Size and format.
3. Choose the resolution you want.
4. Tap Save. Samsung notes that large or high-resolution videos can take a few minutes to save (Samsung).

On any iPhone or Android, with an editor

Most editing apps set the resolution when you export. In CapCut on a phone, tap the resolution label next to the Export button. You can choose 720p or 1080p, plus 2K or 4K if your phone supports them. CapCut also says you cannot export in 4K if all your clips are 1080p or lower, and that many mid-range phones top out at 1080p or 2K (CapCut).

Exporting at a higher resolution than your footage does not add detail. A 1080p clip exported as 4K gives you a bigger file of the same picture. Pick the resolution the platform actually shows. For a phone screen, that is usually 1080p.

Before you record

On iPhone, the resolution and frame rate for new videos are set in Settings > Camera > Record Video (Apple). If you only ever post 1080p, recording at 1080p saves you the step of scaling down later.

Make the file smaller

File size depends on four things: resolution, frame rate, format and length. You can reduce any of them.

• Lower the resolution. Use the steps above. Going from 4K to 1080p is the biggest single reduction.
• Use the efficient format. On iPhone, Settings > Camera > Formats > High Efficiency records in HEVC. Apple says HEVC compresses better than H.264 and uses less storage while keeping the same visual quality. Most Compatible records in H.264 instead (Apple).
• Lower the frame rate. A talking head rarely needs 60 frames per second. 30 is enough for speech.
• Make it shorter. Every second you cut makes the file smaller and keeps the quality. For a talking-head video, the easiest seconds to lose are dead air, false starts and repeated sentences. Our guide to removing silence without making it sound rushed shows how.

Upside: shortening a clip makes the file smaller without lowering the picture quality. Downside: it only helps when there is something worth cutting. A tight 40-second clip needs a lower resolution instead.

Shortening is where slicecut fits, if your video is you talking. You strike words and pauses in the transcript, and the export renders on the phone at source quality, so a 4K take stays 4K and only the cut parts are gone. slicecut does not crop or change the resolution, so for the shape or pixel count, use the tools above.

Edit video on iPhone or Android: where size fits in the order

Whichever phone you edit on, the order matters. Each export compresses the video again, and each pass loses a little quality. Do the size changes in one go at the end:

1. Cut first: trim the start and end, take out mistakes and pauses.
2. Crop to the shape the platform wants.
3. Export once, at the resolution the platform shows.

If you need the cutting steps for your phone, see editing video on iPhone with Photos, iMovie and free apps and editing video on Android with Google Photos and free editors.