File Size & Duration Checker
Check a media file's exact size and duration, then see how long it would take to transfer on a typical connection.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: MP3, WAV, FLAC, M4A/AAC, OGG, Opus, MP4, MOV, MKV, WebM
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | MP3, WAV, FLAC, M4A/AAC, OGG, Opus, MP4, MOV, MKV, WebM |
|---|---|
| Produced output | An inspection report with a downloadable JSON file |
| Processing | Web Audio API + canvas + native JavaScript encoders |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add the media fileThe exact byte size is read from the file object.
- Read the decoded durationIt comes from decoding the audio or video stream, not from metadata alone.
- Note the data rateThis is what determines whether a stream will keep up.
- Check the transfer projectionsFour connection speeds are shown.
- Download the JSON reportUseful for archiving or comparing files.
About this tool
Two numbers decide whether a file is practical: how big it is and how long it lasts. Together they give the data rate, which is what actually determines whether a stream will buffer or a download will finish before the meeting starts.
This checker reports the exact byte count, the decoded duration, the resulting data rate and the projected transfer time at four connection speeds. It is the page to reach for when someone asks whether a file is too large to email or whether a video will stream reliably.
Features
- Exact byte count with thousands separators
- Decoded duration rather than a metadata estimate
- Data rate in kbps for both audio and video files
- Transfer time projected at four connection speeds
- Container and codec identified alongside the size
- Downloadable JSON report
Frequently asked questions
How long will a file take to download?
Divide the file size in megabits by the connection speed in megabits per second. A 100 MB file is 800 megabits, so at 50 Mbps it takes about 16 seconds. The checker does this for you at four common speeds.
What data rate is needed for smooth streaming?
The connection needs to sustain the file's data rate with headroom. For a 6 Mbps video you want at least 8–10 Mbps available, so that buffering and competing traffic do not cause stalls.
Why does the duration differ from what my player shows?
Players often read the duration from container metadata, which can be approximate for variable-bitrate files. This checker decodes the audio, so its figure reflects the actual sample count.
Is there an email size limit I should aim for?
Most providers cap attachments at 25 MB. The video file size calculator will tell you the bitrate needed to fit that limit for your duration.