How to shrink an MP4 (reduce MP4 file size)

We make OctoZip and the online video compressor, so read this with that in mind. The Mac and Windows steps come from Apple's and Microsoft's own help pages, and the Mac ones were also tried on a Mac running macOS 27.2. We haven't measured file sizes from QuickTime, Finder, Clipchamp or HandBrake, so the sizes below come from the formula. The Mac and Windows steps were checked on 1 November 2026; the HandBrake steps, from its documentation, and YouTube's bitrates on 3 November 2026.

What makes an MP4 file big?

Two things: how many bits each second of video gets (the bitrate) and how many seconds there are. The file size is one multiplied by the other:

Size in MB = bitrate in Mbps × seconds ÷ 8 (the ÷ 8 turns bits into bytes).

A one-minute 1080p phone video at 17 Mbps is 17 × 60 ÷ 8 = 127.5 MB. The same minute at 6 Mbps is 6 × 60 ÷ 8 = 45 MB, and at 1.5 Mbps it is 1.5 × 60 ÷ 8 = 11.25 MB, about a tenth of the original. Sound adds little: at 128 kbps it is about 1 MB a minute.

The bitrate is chosen when the video is encoded. It goes up with resolution and frame rate and with how much moves in the picture, and a newer codec such as HEVC (H.265) needs fewer bits than H.264 for a similar picture. MP4 itself is only the container around the picture and sound tracks, so changing the container or the extension changes the size very little. More in video bitrate explained and HEVC vs H.264.

Which settings make an MP4 bigger?

Resolution and frame rate set how many pixels the bitrate has to cover, the codec sets how efficiently it covers them, and the sound adds a little on top. YouTube's recommended upload bitrates give a fair idea of the scale:

• Resolution matters most: 4K has four times the pixels of 1080p, and the bitrates above run about 4½ to 5½ times higher.
• Frame rate: going from 30 to 60 fps at 1080p takes the bitrate from 8 to 12 Mbps, half as much again.
• Codec: HEVC (H.265) needs fewer bits than H.264 for the same picture. Apple says HEVC offers better compression than H.264 at the same visual quality (Using HEIF or HEVC media), and HandBrake describes H.265 as offering "higher quality encodes and smaller file sizes" than H.264 (Video codecs). H.264 plays on more devices.
• Sound is small: 128 kbps is 0.128 × 60 ÷ 8 = 0.96 MB a minute, and 384 kbps, YouTube's recommendation for stereo, is 2.88 MB.

A worked example: a 3-minute MP4 at 1080p and 60 fps, at 12 Mbps with 384 kbps sound, is (12 + 0.384) × 180 ÷ 8 ≈ 278.6 MB. The same 3 minutes at 720p and 30 fps, at 5 Mbps with 128 kbps sound, is (5 + 0.128) × 180 ÷ 8 ≈ 115.4 MB, about 41% of the size. Real encoders land either side of these figures, because the bitrate also depends on how much moves in the picture.

How small should the MP4 be?

Work back from where it is going. Turn the formula round to get the bitrate that fits: bitrate in Mbps = size in MB × 8 ÷ seconds. A 3-minute video for Gmail's 25 MB limit gets 25 × 8 ÷ 180 = 1.1 Mbps for picture and sound together. That calls for a resolution below 720p, such as 480p. Android's guide to sharing video matches resolution to bitrate: 1080p from about 5 Mbps, 720p between 1.5 and 5 Mbps, and smaller than 720p at 1.5 Mbps or less, because a bigger picture squeezed into too few bits looks worse.

Calculated from the formula above; real files land a little either side, because encoders don't hit a bitrate exactly. Try your own numbers in the video bitrate calculator, and see how many MB a minute of video takes at each resolution.

How do I shrink an MP4 in the browser?

Our free online video compressor works in Chrome or Edge on a phone or a computer. The video is never uploaded: the browser makes the smaller copy on your device, and the copy is always an MP4.

1. Open the online video compressor and tap Choose a video, or drop the file on the page.
2. Pick a setting: Small file (about a third of the resolution), Medium (half), High quality (the same resolution at a lower bitrate) or Target size, then type a size in MB or tap 10, 20, 25, 64 or 100 MB. Each setting shows an estimate of the new size.
3. If you like, pick a Resolution: 1080p, 720p or 480p.
4. Tap Compress video and keep the tab open until it finishes.
5. Play the preview, then tap Download, or Share on a phone.

By the page's own estimate, a minute of 1080p at 17 Mbps with stereo sound (about 129 MB) comes out at about 12 MB with Medium. It does one video at a time, up to about 1–2 GB, and needs a browser that can encode video itself; the page tells you if yours can't.

How do I shrink an MP4 on Android?

OctoZip, our free app, compresses videos on the phone and never uploads them. It has presets rather than a size in MB.

1. Open OctoZip and tap Pick a video, or share the video to OctoZip from another app.
2. Under Quick Compression, choose Small file (easy share) (a third of the resolution), Medium file (half) or Best Quality (the original resolution), and tap Apply.
3. Check that Output format is on MP4. It starts on the source's own format, so for an MP4 it already is.
4. Tap Start Compression. It works without an internet connection.
5. Tap Compare to check the result, then Save compressed video ▸ Save as new video to keep both files.

The free version compresses one video at a time, up to 3 GB. OctoZip Pro adds batch compression, files over 3 GB, 8K sources (saved in 4K) and four more presets. It runs on Android 7.0 or later. The full walk-through is in how to compress a video on Android.

GET IT ONGoogle Play

How do I shrink an MP4 on an iPhone?

Trim it in the Photos app, or add it to an iMovie project and save it again at a lower resolution. A shorter clip at the same bitrate is a smaller file, and iMovie's Share options let you pick the resolution. The steps, from Apple's own pages, are in how to compress a video on iPhone; the browser tool above can work there too in Safari, more slowly, though it sometimes stops part way.

How do I shrink an MP4 on a Mac without installing anything?

macOS has two built-in ways, both from Apple, and both save a QuickTime movie (.mov) rather than an MP4. Apple's own guide says QuickTime Player "doesn't export movies as MP4 videos". Most apps accept a .mov; if you need an .mp4, use the Terminal command below or the browser tool above.

QuickTime Player

1. Open the MP4 in QuickTime Player.
2. Choose File ▸ Export As, then 1080p, 720p or 480p. Sizes larger than your video are dimmed.
3. For 1080p, Smaller File Size saves HEVC and Greater Compatibility saves H.264. 720p and 480p are always H.264.
4. Name the file, choose where it goes and click Save.

Source: Apple, Export movies to other file formats and resolutions using QuickTime Player on Mac.

Finder

Control-click the video in Finder and choose Encode Selected Video Files (Apple describes it in its QuickTime Player automation tips; if it isn't in the first menu, look under Services). Pick a smaller setting, such as H.264 720p. On our Mac (macOS 27.2) the settings run from H.264 480p up to HEVC 8K, plus Apple ProRes, and each video setting saves a .mov.

Terminal, if you need an MP4

macOS also includes a command-line tool, avconvert. Its manual page says the output file's extension decides the file type, so a name ending in .mp4 gives an MP4: avconvert -s input.mp4 -p Preset1280x720 -o smaller.mp4 makes a 720p copy. Preset960x540 and Preset640x480 go smaller, and avconvert -h lists every preset. We ran that command on macOS 27.2 and got a 720p H.264 MP4.

How do I shrink an MP4 on Windows?

Clipchamp is the built-in video editor in Windows 11, according to Microsoft; on Windows 10 you get it from the Microsoft Store. It saves MP4 files.

1. Type Clipchamp in the search box on the taskbar and open it. It asks you to sign in with a Microsoft account.
2. Start a new video, import your MP4 and drag it onto the timeline.
3. Select Export at the top right and choose 720p or 480p. Microsoft calls 1080p "the largest free resolution".
4. The new MP4 saves to your computer, usually in Downloads.

Clipchamp's export choices are resolutions, not a size in MB, so check the new file and go one resolution lower if it is still too big. The old Video Editor in the Photos app is gone, Microsoft says, so guides that use it no longer apply. Sources: Microsoft Support, Create films with a video editor, Exporting and saving a video in Clipchamp, How to choose the right export resolution and What is Clipchamp?

How do I reduce an MP4's size with HandBrake?

HandBrake is a free, open-source video transcoder for Linux, Mac and Windows, and its "primary purpose is to convert videos from supported source formats to MP4, MKV, or WebM format" (About HandBrake). It is a separate download, not built in, and gives more control than the tools above.

1. Click Open Source and choose the MP4, or drag it onto HandBrake's window.
2. Pick a preset. Fast 1080p30 is the default; Fast 720p30 or Fast 480p30 bring the picture down further. These General presets save MP4, and they scale a bigger video down and cap its frame rate, so a 1080p video at 60 fps becomes 720p at 30 fps with a 720p30 preset (Official presets).
3. For a smaller file at the same resolution, move the quality control on the Video tab a few steps to the left. With the x264 and x265 encoders a higher RF number means lower quality and a smaller file; HandBrake recommends RF 20–24 for 1080p and RF 19–23 for 720p (Adjusting quality).
4. Check the destination (Save As is the file name, To the folder), then click Start.

That constant-quality setting gives an even picture, but HandBrake says the output size "is unpredictable and varies from source to source". When the file has to fit a limit, its average bitrate mode lets "you control the size of the output file but give up control over the video's quality" (Constant quality vs average bit rate, a page HandBrake marks as a draft). Work the bitrate out first: for a 3-minute video and Gmail's 25 MB, 25 × 8 ÷ 180 ≈ 1.1 Mbps in total, so with 96 kbps sound the picture gets about 1,000 kbps, which calls for 480p or smaller. HandBrake always re-encodes the video; it never copies it across unchanged.

Does zipping an MP4 make it smaller?

Barely. The picture inside an MP4 is already compressed, so a ZIP archive finds little left to remove, and the person you send it to has to unzip it before they can play it. For video, "file compression" in practice means a lower bitrate or resolution, as above.

Will shrinking an MP4 lower its quality?

A little, because a smaller file holds less detail. A lower resolution at a sensible bitrate usually looks cleaner than full resolution squeezed into too few bits, which is why Small file and Medium lower the resolution as well. Each re-encode loses a bit more, so start from the original rather than a copy you have already shrunk. More in does compressing a video reduce quality? and can you compress a video twice?

What these tools can't do

• None of them is lossless: each one re-encodes the video.
• The online compressor does one video at a time, up to about 1–2 GB, and needs recent Chrome or Edge. Safari is slower and sometimes stops part way.
• OctoZip has no target-size option and can't trim; batch compression is in OctoZip Pro.
• QuickTime Player and Finder save .mov files. Clipchamp needs a Microsoft account and offers resolutions, not a size in MB.
• HandBrake's constant-quality sizes vary from video to video; use its average bitrate mode when a limit matters.
• We haven't measured file sizes from QuickTime, Finder, Clipchamp or HandBrake, so this page gives none for them.

Related

• Free online video compressor (no upload)
• How do I compress a video to a specific size?
• What bitrate fits my file size?
• MP4, MOV or MKV: which video format should I choose?
• Can I turn a MOV or MKV video into MP4 on Android?
• How do I compress a MOV file?
• How do I compress a video on iPhone?