Video Bitrate and File Size Calculator
Calculate video file size from bitrate and duration, or the required bitrate to hit a target file size. Includes resolution recommendations from 720p to 8K and upload-limit checks for Douyin, Bilibili, Xiaohongshu, WeChat Channels, and Kuaishou. Built for Chinese short-video creators and editors preparing 4K uploads within platform file caps.
Regional Rule Context
China Rates and Rules
China platform upload caps 2026: Douyin 4 GB / 30 min / 25 Mbps. Bilibili 16 GB / no time cap / 100 Mbps, supports H.265 and AV1. Xiaohongshu 1 GB / 15 min / 15 Mbps. WeChat Channels 512 MB / 60 min / 10 Mbps. Kuaishou 2 GB / 57 min / 20 Mbps. Recommended bitrates (H.264, 30fps): 720p 2.5 to 7.5 Mbps, 1080p 5 to 12, 4K 25 to 68, 8K 80 to 200.
Enter Values
Leave default and use Mode 0 to compute file size. Ignored in Mode 1.
Used only in Mode 1 to compute required bitrate
Result
Enter values above and click Calculate to see your result.
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Video bitrate and file size calculator for Chinese short-video creators in 2026. Computes file size from bitrate and duration (Mode 0), or solves for required bitrate given a target file size (Mode 1). The underlying formula is file size in MB equals bitrate in Mbps times duration in seconds divided by 8. Recommended bitrates by resolution at 30fps H.264: 720p 2.5 to 7.5 Mbps, 1080p 5 to 12, 4K UHD 25 to 68, 8K 80 to 200. Chinese platform caps in 2026: Douyin 4 GB file size, 30 minute duration, 25 Mbps soft bitrate cap; Bilibili 16 GB, no duration cap, 100 Mbps, supports H.265 and AV1 codecs for better compression; Xiaohongshu 1 GB, 15 min, 15 Mbps cap which is tight for 4K content; WeChat Channels 512 MB, 60 min, 10 Mbps cap which is the strictest for 4K; Kuaishou 2 GB, 57 min, 20 Mbps. Using H.265 codec halves file size at the same visible quality, which is often the only way to fit 4K into WeChat Channels or Xiaohongshu limits.
Disclaimer: This calculator uses publicly available rules effective as of Jan 1, 2026 (version 1.0). Results are for informational purposes only. Always verify with official sources or a qualified professional. Last reviewed: Apr 23, 2026.
Formula
Video file size in megabytes equals the bitrate in megabits per second times the duration in seconds, divided by 8 (since 8 bits = 1 byte). Rearranging solves for required bitrate given a target file size.
China FAQs
What bitrate do I need to fit a 4K video under Douyin limit?
Douyin caps uploads at 4 GB with a 25 Mbps soft bitrate ceiling. For a 30-minute 4K video, that is 4 x 1024 x 8 / 1800 = about 18.2 Mbps maximum to fit the file size limit, well within the 25 Mbps bitrate cap. For shorter videos, you can use higher bitrates up to 25 Mbps without size concern.
How big is a 4K video at 45 Mbps for 3 minutes?
Using the formula 45 x 180 / 8 = 1,012.5 MB, about 1 GB. That fits inside Douyin 4 GB and Bilibili 16 GB but not WeChat Channels 512 MB. For WeChat, drop bitrate to about 22 Mbps (which starts to show visible compression on 4K) or re-encode at 1080p.
Why can I not upload my 4K video to Xiaohongshu?
Xiaohongshu caps uploads at 1 GB per video. A 4K video longer than about 3 to 4 minutes at recommended bitrate (35 to 45 Mbps) will exceed 1 GB. Options: re-encode at lower bitrate (under 15 Mbps, which forces 4K to soften visibly), use H.265 to halve file size at the same quality, or drop to 1080p. Most Xiaohongshu creators stick with 1080p at 8 Mbps for the best size-quality balance.
What is the best codec for China platform uploads?
H.264 is the universal safe default, supported by every Chinese platform. H.265 (HEVC) delivers the same visible quality at roughly half the file size and is supported by Bilibili and Douyin. AV1 is Bilibili-only and even more efficient. WeChat Channels and some older playback paths do not reliably support H.265 yet. Use H.264 as default and H.265 for 4K uploads where file size matters.
Does this calculator account for audio track size?
No. The formula computes video bitrate only. Audio adds about 0.1 to 0.2 MB per second (128 to 192 kbps AAC stereo). For a 3-minute video, that is roughly 25 to 35 MB of audio on top of the video size. For short videos under 60 seconds, audio overhead is negligible; for long-form on Bilibili, factor it in when calculating precise file sizes.
What frame rate does this assume?
30fps. For 60fps content, multiply the recommended bitrate by about 1.5. 4K 60fps needs 45 to 100 Mbps to look clean, which often exceeds platform caps. 60fps 1080p (5 to 12 Mbps x 1.5 = 7.5 to 18 Mbps) is a common workaround for sports and gaming content on Bilibili.
How does WeChat Channels compare to Douyin for 4K uploads?
WeChat Channels has the strictest 4K caps (512 MB and 10 Mbps), which makes 4K uploads essentially impossible beyond 6 to 7 minutes even with aggressive H.265 compression. Douyin is much more permissive (4 GB and 25 Mbps) and handles 4K well up to 30 minutes. For serious 4K work, Bilibili (16 GB, 100 Mbps, H.265/AV1 support) is the best home.
How do I add this Video Bitrate and File Size Calculator to my site?
Absolutely. Use the "Embed" option above to tailor the dimensions, color scheme, and styling to match your site. Copy the generated iframe snippet and drop it into your HTML, WordPress editor, or any CMS. There is no cost and no account required. See calculory.com/services/embed-calculators for a step-by-step walkthrough.
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