Work out how large a video will be before you export it. Enter duration and bitrate, get megabytes — checked against the upload caps that actually bite.
Unlimited — runs in your browser
How It Works
How long the finished video runs.
Video bitrate in Mbps, plus audio bitrate in kbps. Both come from your export settings.
The estimated file size, flagged against platform upload limits so you know before you export rather than after.
The formula is simpler than it looks: file size equals bitrate multiplied by duration. Bitrate is how many bits of data each second of video uses, so a 10 Mbps video running 60 seconds contains 600 megabits — about 75 megabytes, once you divide by 8 to convert bits to bytes.
Resolution does not enter the formula directly, which surprises people. A 4K video is bigger than a 1080p one only because you would normally give 4K a higher bitrate — encode both at 10 Mbps and they produce identical file sizes. Resolution drives the bitrate you should choose; bitrate drives the size.
Audio adds a small constant on top. At 128-256 kbps it is typically 1-3% of a video file's total, negligible for a short clip and worth including for anything long.
Why Use This Tool
Find out you are over a platform's cap before spending twenty minutes on an encode.
Results are flagged against the limits that actually reject files, TikTok's 287.6MB included.
Audio bitrate is part of the calculation rather than an afterthought.
Pure arithmetic, no account, no cap.
Know your size budget? Read the bitrate that fits it.
Check from your phone mid-edit.
Multiply the bitrate by the duration, then divide by 8 to get bytes from bits. A 10 Mbps video for 60 seconds is 600 megabits, which is roughly 75MB. Add audio on top.
No — bitrate determines size, not resolution. A 4K and a 1080p file encoded at the same bitrate are the same size. Higher resolutions only tend to be bigger because they need more bitrate to look good.
287.6MB for web uploads. It is an unusual number because it is a byte-level cap rather than a round megabyte figure, and it catches people exporting long clips at high bitrates.
Very little. At 128-256 kbps, audio is typically 1-3% of the total for a video file.
Close, for constant-bitrate encodes. Variable-bitrate encoding varies bitrate by scene complexity, so real output lands near the estimate rather than exactly on it.
Lower the bitrate first — it is the direct lever. Shortening the video works proportionally. Dropping resolution only helps because it lets you justify a lower bitrate.
If you are calculating file sizes by hand, you are compensating for an export step that does not know where the video is going. ShortsHero exports every clip at the spec of the platform it is destined for.
See platform-spec exportsFree to start · No credit card required
Keep Going
Find the right export bitrate for any resolution and frame rate. Recommended settings for YouTube, TikTok, Reels and Shorts — free and instant.
Enter a video duration and see instantly which platforms accept it, which will reject it, and how much you need to cut. Current limits for every major platform.
Free video aspect ratio calculator. Enter your source size for exact 9:16, 1:1, 4:5 and 16:9 dimensions, plus how much of the frame each crop throws away.
Enter your recording length and format to see how many short clips it realistically contains, how many editing hours that costs by hand, and the cost per clip.
Estimated size
76.4 MB
Video track
75.0 MB
Audio track
1.4 MB
1.9% of total
TikTok (web)
Cap 287.6 MB
Cap 4 GB
YouTube (unverified)
Cap 128 GB
Size is bitrate × duration ÷ 8. Resolution does not enter the formula — a 4K and a 1080p export at the same bitrate are the same size. Variable-bitrate encodes land near this estimate rather than exactly on it, since VBR spends more bits on complex scenes.