Free tool
Video File Size Calculator
Enter a bitrate and a duration and get the file size before you export. 8 Mbps for 60 seconds is a 60 MB stream, about 60.6 MB with the estimated container overhead, and you can see which platform limits that clears.
Last updated: 2026-10-25
Most export dialogs ask for a bitrate, not a file size, and the size follows from it: megabits per second times seconds, divided by eight, gives megabytes. This calculator does that sum for the total bitrate, video plus audio, and counts 1 MB as 1,000,000 bytes.
On top of the audio and video, the MP4 or MOV wrapper adds a little for headers and the sample index. No platform publishes that number, so the calculator adds an estimated 1 percent, a round and slightly pessimistic figure for a file with one video and one audio track. The result is an estimate, not a promise about the exact bytes your encoder will write.
The estimate is then checked against the published size, duration and bitrate limits for every video format in our spec tables. An X post video stops at 512 MB and 140 seconds, an Instagram Story at 100 MB and 60 seconds, and Instagram Reels at 300 MB in the publishing API that scheduling tools use, so the same export can fit one and miss the next. Each format also shows the highest bitrate that still fits. It all runs in your browser.
Video plus audio: the total your editor shows on export.
Length
An estimate. MP4 and MOV wrappers usually add about 1%, and the real number depends on the file.
Estimated file size
60.6 MB
60.0 MB of video and audio, plus 0.6 MB of overhead
Does it fit?
Each video format is checked against its file size, length and bitrate limits.
| Format | Max size | Result | Highest bitrate that fits |
|---|---|---|---|
| Instagram Reel | 300 MB | Fits | 25.0 Mbps |
| Instagram Story | 100 MB | Fits | 13.2 Mbps |
| Instagram Carousel | 300 MB | Fits | 39.6 Mbps |
| Facebook Feed video | 4096 MB | Fits | 25.0 Mbps |
| Facebook Reel | 4096 MB | Fits | 25.0 Mbps |
| Facebook Story | 100 MB | Fits | 13.2 Mbps |
| Threads Post video | 1024 MB | Fits | 25.0 Mbps |
| Threads Carousel | 1024 MB | Fits | 135.2 Mbps |
| LinkedIn Native video | 5120 MB | Fits | 675.9 Mbps |
| X Post video | 512 MB | Fits | 25.0 Mbps |
| TikTok Video post | 4096 MB | Fits | 540.7 Mbps |
| YouTube Short | 262144 MB | Fits | 34606.5 Mbps |
| YouTube Standard video | 262144 MB | Fits | 34606.5 Mbps |
| Pinterest Video Pin | 2048 MB | Fits | 25.0 Mbps |
Platform limits checked on 2026-07-31
Tips
- Size for the tightest platform first. If one export has to go to X and TikTok, the 512 MB X limit decides the bitrate, not the 4 GB TikTok allows.
- Add the audio to the video bitrate before you calculate. The file holds both tracks, so a size worked out from the video bitrate alone always comes in low.
- Leave headroom under a hard limit. Encoders aim at an average, so a busy clip can come out a little larger than the target, and a file that lands right on the limit is the one that gets rejected.
Frequently asked questions
How do you calculate video file size?
Multiply the total bitrate in megabits per second by the duration in seconds and divide by 8. That gives megabytes: 8 Mbps for 60 seconds is 60 MB. Then add a little for the container, which this calculator estimates at 1 percent, so the example comes to about 60.6 MB.
Is the calculated size exact?
No, it is an estimate. The stream size is simple arithmetic, but the container overhead is an assumption, and a variable bitrate encode rarely hits its target exactly. Use the number to choose a bitrate, then check the finished file with the video size checker.
Why does my computer show a smaller size than the calculator?
Some file managers count a megabyte as 1,048,576 bytes, while this calculator uses 1,000,000, so the same file shows a smaller number there. Platform limits are compared against the larger decimal figure here, which keeps the check on the cautious side.
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