Video File Size Calculator
Estimate a video's size from its bitrate and duration — or work out the bitrate you need to fit a target limit.
Convert with this tool
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
| Input | Numbers you type — nothing is calculated until you change a value |
|---|---|
| Output | A live result table, recalculated on every keystroke |
| Processing | Plain arithmetic in this tab — instantaneous and offline |
About this tool
Two questions come up constantly in video work: how big will this be, and what bitrate do I need to fit inside a limit? They are the same equation solved in opposite directions, and this calculator answers both.
Enter the bitrate and duration for a size estimate, or choose a target limit and the tool tells you whether your current bitrate fits and, if not, what it would need to be. The last row shows the same content at 45 percent of the size, which is a realistic figure for HEVC at equivalent quality.
Features
- Size estimate from bitrate and duration
- Five common size limits including a 25 MB email attachment
- The bitrate needed to fit a limit that you currently exceed
- Percentage of the limit used, so you can see your headroom
- HEVC comparison at roughly 45 percent of the H.264 size
- Total bit count for precise planning
Frequently asked questions
How do I get a video under 25 MB for email?
Enter your duration and select the 25 MB limit. The calculator tells you the bitrate you need. For a three-minute clip that is around 1,100 kbps, which is achievable at 720p with a higher CRF.
Why is my file larger than the estimate?
The estimate assumes a constant bitrate. Variable-bitrate encoders exceed the average on complex scenes, and the container, audio track and metadata all add overhead. Treat the figure as a close approximation rather than an exact prediction.
Is HEVC really half the size?
At equivalent perceived quality, HEVC typically needs 40–50 percent of the bitrate H.264 needs. The trade is much slower encoding and patchier hardware support on older devices.
Does the audio bitrate matter at this scale?
For long files it does. A 320 kbps audio track over an hour is 144 MB on its own, which can be a significant fraction of the total.