ClipShrink
Bitrate, Duration & Platform Limit Reference

Video File Size & Duration Calculator

Find out how long a 10MB, 16MB, 20MB, 25MB, or 50MB video can be at 720p, 1080p, and 4K—and calculate the exact bitrate needed to fit your clip under any upload limit.

Estimated Video Length in 25 MB
2 min 38 sec

At 1200 kbps video + 96 kbps AAC audio (720p HD Standard Video (30fps)), a 25 MB file holds approximately 2 min 38 sec of footage.

Bitrate for Your Clip Length:60s (1 min)

To fit a 60s video under 25MB, ClipShrink encodes at 2907 kbps video + 96 kbps audio (~22MB output).

Compress for Gmail (25MB) Now

How Long is a 10MB, 25MB, or 50MB Video? (Cheat Sheet)

Compare how much video duration fits inside common file size limits before and after H.264 compression.

File SizeRaw 4K Camera1080p Full HD720p HD (Standard)720p Screen / SlidesCompressor
8 MB
Discord Classic Limit
3 seconds24 seconds50 seconds1 min 35 secShrink
10 MB
Slack / Job Portals
3.7 seconds31 seconds1 min 03 sec1 min 58 secShrink
16 MB
WhatsApp Media Limit
6 seconds50 seconds1 min 41 sec3 min 08 secShrink
20 MB
Discord Free / Outlook
7.4 seconds1 min 02 sec2 min 06 sec3 min 55 secShrink
25 MB
Gmail Attachment Limit
9.2 seconds1 min 18 sec2 min 38 sec4 min 54 secShrink
50 MB
Discord Nitro Basic / Forms
18.5 seconds2 min 36 sec5 min 16 sec9 min 48 secShrink
100 MB
Canvas / Blackboard LMS
37 seconds5 min 12 sec10 min 32 sec19 min 36 secShrink

Why Raw Phone Videos Are Huge

iPhones and Android phones record at 15,000 to 35,000 kbps so the camera sensor can write frames in real time without overheating. Re-encoding in H.264 at 1,200 kbps shrinks the file by ~90% while keeping 720p HD clarity.

The Exact Bitrate Formula

File size is determined by (Bitrate kbps × Seconds) / 8192. Changing resolution (e.g., 1080p to 720p) only reduces file size if the encoder also lowers the target bitrate.

Why Email Needs a 10% Buffer

Gmail (25MB) and Outlook (20MB) encode binary attachments into Base64 text during transit, adding overhead. Always target ~22MB for Gmail and ~18MB for Outlook so your email doesn't bounce.

Frequently Asked Questions

How long is a 25MB video?
On an uncompressed iPhone 4K camera (~22 Mbps), 25MB is only 9 seconds of video. However, when compressed to standard 720p HD (1.2 Mbps H.264), a 25MB MP4 holds about 2 minutes and 38 seconds of regular camera footage, or nearly 5 minutes of low-motion screen recording and slides.
How long is a 10MB video?
At raw 4K smartphone settings, a 10MB video is less than 4 seconds long. Once compressed to 720p HD using H.264, a 10MB file holds approximately 60 to 65 seconds of standard video, or up to 2 minutes of screen capture.
How long is a 50MB video?
A 50MB MP4 file holds roughly 2 minutes and 36 seconds of 1080p Full HD video (2.5 Mbps), 5 minutes and 15 seconds of 720p HD video (1.2 Mbps), or nearly 10 minutes of 720p presentation and screen recording footage.
How is video file size calculated from duration and bitrate?
Video file size depends strictly on two numbers: Duration (in seconds) and Total Bitrate (video + audio in kilobits per second), divided by 8,192 (since 8,192 kilobits = 1 Megabyte). The formula is: File Size (MB) = (Total Bitrate kbps × Duration seconds) / 8192. Resolution and frame rate only affect how sharp the video looks at that bitrate.
What are the video attachment size limits for Gmail, Outlook, WhatsApp, and Discord?
Gmail allows up to 25MB per email. Microsoft Outlook and Exchange default to 20MB. WhatsApp caps standard video media attachments at 16MB. Discord's free upload limit is 20MB (raised from 10MB in August 2026, and 8MB prior to 2023), while Discord Nitro Basic allows 50MB.