# How to compress a video for WhatsApp or email: resolution, bitrate and file size explained > A video’s size is bitrate times length, and nothing else. At 1 Mbps every minute is about 7.5 MB, so 25 MB holds only 3 minutes. How to pick a resolution and quality in the video compressor, a table of how long a video fits in an email, why the compression takes as long as the video, and what to do when the result is not smaller. Published 2026-10-23 by Toolcloak. 4 minute read. Original: https://toolcloak.com/articles/how-to-compress-a-video-for-whatsapp-or-email-resolution-bitrate-and-file-size-explained Related free tool: [Video Compressor](https://toolcloak.com/tools/video-compressor) The video is 300 MB and the email limit is 25. The form wants under 50. The WhatsApp upload is crawling. You can try random settings until something works, or you can know one equation. A video file’s size is its **bitrate multiplied by its length**. Everything else, the resolution, the quality, the format, is just a way to change the bitrate. Once you see that, you can choose settings that hit a size on purpose. > **In short** > - **Size (MB) ≈ bitrate (Mbps) × seconds ÷ 8.** At 1 Mbps, one minute is 7.5 MB. > - **Lower resolution and lower quality both reduce bitrate.** Pick the combination, then check the number. > - **A short clip is the easiest win.** Trim first, then compress. > - **The compressor works in real time,** so a 10-minute video takes about 10 minutes. Keep the tab open and in front. ## The one equation > **File size from bitrate:** Megabytes = megabits per second × seconds ÷ 8. A 5-minute video at 1.5 Mbps is 1.5 × 300 ÷ 8 = 56 MB. The 8 is there because there are 8 bits in a byte. Sound adds a little more, usually under 1 MB a minute. This is why a video’s size does not depend on the file format, only on how many bits per second it uses. This also clears up a common mix-up. Network speeds use **megabits** (Mbps), and file sizes use **megabytes** (MB). One is eight times the other. The [data storage units guide](https://toolcloak.com/articles/why-a-1-tb-drive-shows-931-gb-kb-kib-mb-and-mbps-explained) explains it in full. Try it: [Video Compressor](https://toolcloak.com/tools/video-compressor). Choose a video, pick a resolution and a quality, and download the smaller file. The video stays on your device. ## What the settings mean The tool gives you two choices. **Resolution** sets the picture’s width: keep original, 1280 (720p), 854 (480p), 640 (360p) or 426 (240p). **Quality** sets the bitrate the compressed video may use, from 2.5 Mbps down to 0.3 Mbps. The default is 480p at 1 Mbps, a balanced choice for phones. | Quality choice | Bitrate | Size per minute | Size per 10 minutes | | --- | --- | --- | --- | | High | 2.5 Mbps | about 18.8 MB | about 188 MB | | Good | 1.5 Mbps | about 11.3 MB | about 113 MB | | Balanced (default) | 1.0 Mbps | about 7.5 MB | about 75 MB | | Small | 0.6 Mbps | about 4.5 MB | about 45 MB | | Smallest | 0.3 Mbps | about 2.3 MB | about 23 MB | *Worked from the bitrate equation, before about 0.5 to 1 MB a minute for sound. Real files can be a little over or under.* **Approximate size of a 10-minute video by quality (MB)** | | MB | | --- | --- | | High 2.5 | 188 MB | | Good 1.5 | 113 MB | | Balanced 1.0 | 75 MB | | Small 0.6 | 45 MB | | Smallest 0.3 | 23 MB | *Halving the bitrate halves the file. That is the whole lever.* ## How long a video fits in an email Most email services limit attachments to about 25 MB. Here is the longest video that fits at each quality, before sound is added, so aim a little under these. | Quality | Bitrate | Longest video in 25 MB | | --- | --- | --- | | High | 2.5 Mbps | about 1 minute 20 seconds | | Good | 1.5 Mbps | about 2 minutes 10 seconds | | Balanced | 1.0 Mbps | about 3 minutes 20 seconds | | Small | 0.6 Mbps | about 5 minutes 30 seconds | | Smallest | 0.3 Mbps | about 11 minutes | *Calculated as 25 MB × 8 ÷ bitrate. Add a margin for sound and for slight differences in the final file.* **Hitting a size on purpose** 1. **Know the limit.** For example, 25 MB for email, or the number the form says. 2. **Know the length.** Check the video’s duration in seconds. 3. **Work out the bitrate.** Bitrate = size × 8 ÷ seconds. For 25 MB over 240 seconds, about 0.8 Mbps. 4. **Pick the next setting down.** Choose the quality at or below that: here, Small at 0.6 Mbps. *Always round down. A file just over the limit is rejected.* ## Resolution or quality: which first? **Two ways to cut size** | Lower the resolution | Lower the quality | | --- | --- | | Smaller picture | More blockiness | | 720p to 480p cuts pixels by more than half | Cuts the bits spent on every frame | | Looks fine on a phone screen | Fast motion and dark scenes suffer first | | Text and fine detail get softer | Can look smudgy on large screens | *For a phone, a lower resolution with a decent bitrate usually looks better than a high resolution squeezed into a tiny bitrate. The two settings work together: if you drop the resolution, you can often drop the bitrate too.* - **For WhatsApp and phone viewing:** 480p with Balanced or Small is a good start. - **For a lecture or talk with slides:** keep 720p if the text must be readable, and use Small or Balanced. - **For a form upload with a strict limit:** work out the bitrate from the equation and take the next setting down. - **If you only need the sound:** extract the audio instead. A video to MP3 tool gives a far smaller file. ## Trim first, then compress Cutting out the part nobody needs is the best compression there is, because it removes bits without touching quality. Trim the start and end with a video trimmer, then compress what is left. A 4-minute clip trimmed to 2 minutes at the same quality is half the size. ## What to expect while it works - **It takes about as long as the video.** The compressor plays the video and records it again at the new settings. A 6-minute video takes around 6 minutes. - **Keep the tab open and in front.** Switching away or locking the phone can pause or stop the job in some browsers. - **You can stop early** and keep what has been done so far. - **The result can be larger than the original.** If the video was already small, re-encoding may not shrink it. The tool says so. Choose a lower resolution or quality, or leave the file as it is. - **The file you get depends on your browser.** The tool tells you the file type when it is ready. > **Check before you send:** Play the result for a few seconds in the middle and at the end, and look at the size shown beside the original. Then send it. If a form rejects it, the limit may count differently, so keep it comfortably under. ## Sharing: a note on limits Apps change their limits over time, and some re-compress videos on their own when you send them as a normal video. Sending a file as a document keeps it as it is but may have its own size cap. Check the current limit in the app you use. For images that go with it, the [image compression guide](https://toolcloak.com/articles/why-your-4mb-photo-is-really-a-400kb-photo) and the [20 KB to 200 KB guide](https://toolcloak.com/articles/how-to-compress-an-image-to-20-kb-50-kb-100-kb-or-200-kb-for-forms-and-exam-portals) work the same way, and for documents see the [PDF compression guide](https://toolcloak.com/articles/how-to-compress-a-pdf-why-files-are-so-big-and-how-to-get-under-an-upload-limit). To send a chat link along with it, use the [WhatsApp link guide](https://toolcloak.com/articles/how-to-make-a-whatsapp-link-that-opens-a-chat-with-a-ready-message-no-need-to-save-the-number). Related guides: [how to convert video to MP3](https://toolcloak.com/articles/how-to-convert-video-to-mp3-extract-audio-from-an-mp4-pick-the-bitrate-and-know-the-file-size-before-you-start). ## Frequently asked questions ### How do I compress a video without losing quality? Some loss is unavoidable, but you can keep it small by trimming the clip first, lowering the resolution before the bitrate, and avoiding extreme quality settings. A phone-sized 480p video at about 1 Mbps looks good for most uses. ### Video ka size kaise kam kare? Video compressor me video chunein, resolution (jaise 480p) aur quality (jaise Balanced) select karein aur Compress dabayein. Size ka rule: bitrate (Mbps) × seconds ÷ 8 = MB. Pehle video ko trim kar lein to aur bhi chhota hoga. ### How do I get a video under 25 MB for email? Work out the bitrate: size in MB × 8 ÷ seconds. For 240 seconds, about 0.8 Mbps, so choose the Small setting (0.6 Mbps). Trim the video if it is still too big. ### What determines a video’s file size? Its bitrate and its length. Size in MB is roughly bitrate in Mbps times seconds divided by 8. Resolution and quality settings change the bitrate. ### Why is my compressed video not smaller? If the original was already efficiently encoded, re-encoding at a similar bitrate will not shrink it. Choose a lower resolution or a lower quality. ### Why does compressing take so long? The tool re-records the video as it plays, so it takes about as long as the video itself. Keep the tab open and in front until it finishes. ### Is my video uploaded when I compress it? No. The video is processed on your own device, in your browser. ### Is Mbps the same as MB? No. Mbps is megabits per second, used for speed and bitrate. MB is megabytes, used for file size. One byte is eight bits, so a size in MB is the bitrate times seconds divided by 8.