What's container overhead?

MP4, MOV, and MKV containers wrap the raw video and audio streams with index tables, codec metadata, chapter markers, and timestamp information — usually 1–3% of the total file size. For sizing decisions that overhead is negligible, but for a 10 GB master it can be 100–300 MB, so it's worth rounding up in tight-fit situations. The formula in this tool implicitly absorbs that overhead into rounding.

How much does the audio bitrate affect total size?

192 kbps stereo audio works out to about 1.4 MB per minute, or 84 MB per hour. That's small next to even modest video bitrates, but it adds up on long files — a two-hour edit at 192 kbps adds roughly 170 MB of audio alone. If you're squeezing a file under a hard limit, dropping audio from 320 to 128 kbps can buy you tens of megabytes without anyone noticing the difference.

Can I reduce file size after exporting?

Yes — use the Video Compressor at /tools/video-compressor to re-encode at a lower bitrate or with a quality-based preset. A second-pass re-encode is always worse than getting the bitrate right at export, but it's the practical fix when you need a file to fit a tight upload limit. Pair it with the Video Bitrate Calculator at /tools/video-bitrate-calculator to pick a target Mbps that lands at the size you need.

Free tool · runs in your browser

Video File Size Calculator

Enter a duration, a video bitrate, and an audio bitrate — get an MB and GB estimate, the full formula, and an at-a-glance check against the upload limits of major platforms.

HoursMinutesSeconds

Video bitrate (Mbps)Audio bitrate (kbps)

Estimated file size

614.4 MB

In gigabytes

0.60 GB

Formula

(8 Mbps + 192 kbps / 1000) × 600 s ÷ 8 ÷ 1024 = 0.600 GB

Combined stream: 8.192 Mbps. Container overhead (MP4/MOV/MKV) adds another 1–3%, which is rolled into the rounding here.

Upload limits

Over limit.WhatsApp — ~64 MB per video960% of limit
Over limit.TikTok — ~287 MB upload214% of limit
Over limit.Twitter/X — ~512 MB on free tier120% of limit
Fits.YouTube — 256 GB / 12 h ceiling — practically unlimited0% of limit

How to use this tool

01
Enter the video duration
Hours:minutes:seconds — match what your editor's timeline shows.
02
Enter the video bitrate
Use the Video Bitrate Calculator if you don't know your target.
03
Check against upload limits
Some platforms have tight limits — the tool shows where your file falls.

Why this matters

Picking an export bitrate without checking the resulting file size is one of the easiest ways to blow past a client's upload cap, fill a drive halfway through a render, or end up with a TikTok clip that gets refused mid-publish. Knowing the size up-front lets you choose between re-encoding, splitting the file, or dropping a quality notch before you commit to a long render — far cheaper than discovering the problem after the fact.

This calculator stays narrow on purpose — duration, video bitrate, audio bitrate — and shows the formula in full so you can sanity-check any other tool's numbers without opening a desktop calculator. The upload-limit grid catches the most common platform ceilings (WhatsApp, TikTok, X, YouTube) so a tight fit doesn't surprise you at upload time. Pair it with the Video Bitrate Calculator to pick the right target Mbps for your resolution and codec before sizing the file.

Related tools

Bitrate Calculator

Find a target video encoding bitrate by resolution, framerate, quality preset, and codec. Deterministic lookup with the math shown.

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Video Storage

Total MB/GB/TB for a video library from video count, average duration, and bitrate. Compares against cloud and drive capacity tiers.

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Video Compressor

Compress any video to a target file size (two-pass) or a CRF quality level in your browser. Hit Discord, email, or WhatsApp limits with no upload.

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FAQ

Resolution determines what's possible — the pixel grid the encoder has to fill — but bitrate decides how many bits actually get spent describing those pixels. A 4K file at 8 Mbps looks worse than a 1080p file at 16 Mbps because the encoder has to smear too few bits across too many pixels. File size on disk is bitrate × duration; resolution only enters the equation through the bitrate you choose to feed it.

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94 free tools covering titles, tags, thumbnails, scripts, captions, embeds, schema, and in-browser video processing.

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How to use this tool

Enter the video duration

Enter the video bitrate

Check against upload limits

Why this matters

Related tools

FAQ

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