Video file size calculator

The formula

A video file is mostly its bitrate multiplied by its length. Add the video and audio bitrates, multiply by the duration in seconds, and divide by 8 to turn bits into bytes:

size in bytes = (video bitrate + audio bitrate) × seconds ÷ 8

A 30-second clip at 8 Mbps of video and 128 kbps of audio is (8,000,000 + 128,000) × 30 ÷ 8 = 30,480,000 bytes: 30.48 MB, or 29.07 MiB. Run it the other way to find the highest bitrate that fits a limit: a 60-second video that must stay under 100 MB, with 128 kbps audio, can average 100,000,000 × 8 ÷ 60 = 13.33 Mbps in total, so 13.20 Mbps of video.

Real files come out a little different. The container adds a small amount on top, and most encoders use a variable bitrate, so a file's average bitrate is what matters. Treat the result as a close estimate and leave a little room under any hard limit.

MB or MiB?

There are two megabytes. A decimal megabyte (MB) is 1,000,000 bytes. A binary one, properly called a mebibyte (MiB), is 1,048,576 bytes, and it is what many operating systems and editors mean when they say MB. The gap grows with size: 4 GB is 4,000,000,000 bytes, while 4 GiB is about 4.29 billion.

None of the platform pages below says which one it means. So the calculator shows both, and checks limits against the decimal reading, which is the smaller number. A file under the decimal limit fits under either. If a file only fits under the binary reading, the row turns amber rather than green.

Upload limits, from each platform's own page

• YouTube: 256 GB or 12 hours, whichever is less. By default, 15 minutes, until you verify your Google Account. From Upload videos longer than 15 minutes.
• TikTok posts: up to 4 GB when posted through TikTok's Content Posting API, which scheduling tools use. Every creator can post 3-minute videos and some can post 5 or 10 minutes; 10 minutes is the longest a developer can send. Frame rate 23 to 60 fps. From TikTok's media transfer guide.
• TikTok in-feed ads: 500 MB or less, up to 10 minutes, bitrate at least 516 kbps, for non-Spark ads. From the auction in-feed ad specs.
• Instagram Reels and Stories: through the Instagram API, a Reel can be 300 MB and 3 seconds to 15 minutes, a Story 100 MB and 3 to 60 seconds. Both: video bitrate 25 Mbps at most, AAC audio at 128 kbps, 23 to 60 fps. From Meta's Instagram media reference.
• Facebook Feed video ads: up to 4 GB, 1 second to 241 minutes. From Meta's Facebook Feed video ad specs.
• X posts: 8 GB and 20 minutes on a default account, 16 GB and 125 minutes with X Premium. From the X media best practices. X video ads: 1 GB max, up to 2 minutes 20 seconds, and X strongly recommends keeping files under 30 MB. From X's creative ad specifications.
• LinkedIn: between 75 KB and 500 MB, three seconds to 30 minutes, MP4, for videos in posts and ads. From LinkedIn's Videos API.
• Pinterest: up to 2 GB, 4 seconds to 15 minutes, H.264 or H.265, for video Pins and ads. From Pinterest's product specs.
• Reddit video ads: 1 GB max, 2 seconds to 15 minutes, 30 fps at most. From Reddit's video ad specifications.

Bitrates worth starting from

The preset buttons fill in YouTube's recommended upload bitrates for standard dynamic range video: 5 Mbps at 720p, 8 Mbps at 1080p, 12 Mbps at 1080p and 48 to 60 fps, and 35 to 45 Mbps at 2160p (4K), with 384 kbps for stereo audio. From YouTube's recommended upload encoding settings. They are a sensible baseline for other platforms too, but check the limit: 45 Mbps is over Instagram's 25 Mbps cap for Reels.

Check a video you already have

Drop a video on the box and the page reads two things on your device: the file's size, and its length, by opening it in a hidden video player. It then shows the average bitrate and checks the real file against every limit. The file is never uploaded. If your browser cannot play the format (some browsers cannot decode HEVC, for example), it can still read the size but not the length, and you can type the length in.

What this calculator does not do

It does not re-encode or compress anything, and it does not check resolution, aspect ratio, codec or frame rate of a file, only its size, length and average bitrate. It uses the numbers each platform publishes, which change from time to time, so each one links to its source. A limit in an ad account or an app can differ from the published figure for some accounts; X, for one, notes that select advertisers can request longer videos.

If you would rather skip the export settings

Hermoso is marketing on autopilot. It makes video ads in 9:16, 1:1 and 16:9, can lay an image ad out again for other sizes or reframe a video to another aspect ratio, and posts or schedules to your own connected channels, refusing a post a platform would reject at the moment you schedule it. See the AI video ad maker and the social media scheduler.

Free tools: Aspect ratio calculator · Social media size guide · TikTok safe zone checker

Frequently asked questions

How do I calculate video file size?

Add the video and audio bitrates, multiply by the length in seconds and divide by 8. A 30-second video at 8 Mbps with 128 kbps audio is (8,000,000 + 128,000) x 30 / 8 = 30,480,000 bytes, about 30.5 MB.

What bitrate fits a 100 MB limit?

Divide the limit in bits by the length, then subtract the audio. For 60 seconds: 100,000,000 x 8 / 60 = 13.33 Mbps in total, so about 13.2 Mbps of video with 128 kbps audio. Leave a little room for container overhead.

Is a platform's MB 1,000,000 or 1,048,576 bytes?

The platform pages cited here do not say. The calculator checks against 1,000,000 bytes, the smaller reading, so a file it passes fits either way, and it flags files that only fit under the larger reading.

What is the maximum file size for Instagram Reels?

Through the Instagram API, 300 MB, 3 seconds to 15 minutes, with video bitrate up to 25 Mbps and 128 kbps AAC audio, per Meta's Instagram media reference. Stories are 100 MB and up to 60 seconds.

Does the tool upload my video?

No. It reads the file's size and plays it in a hidden player on your device to read its length. Nothing is sent anywhere.