Video File Size Calculator
Estimate a video file's size from its length, resolution and bitrate.
How big the file will be
A video file's size is essentially its bitrate — the data used per second — times its length. This estimates the size from the runtime, resolution and bitrate, so you can tell whether a video will fit an upload limit, a storage space, or an email before you export it.
Enter the length, resolution and bitrate to see the estimated size.
The quality-and-size balance
Bitrate is the real driver of both size and quality: more bitrate means more detail and a bigger file, less means a smaller file that can look soft or blocky. Higher resolutions need higher bitrates to look their best, so a 4K clip is far larger than the same length at 1080p. If you have a size limit to hit — a platform's cap, a disc, a mail attachment — the estimate tells you the bitrate to target, and conversely how large a given quality will run. Understanding this turns exporting from guesswork into a deliberate trade-off between quality and file size.
Frequently asked questions
What determines a video's file size?
Mainly its bitrate times its length. Higher bitrate and higher resolution both make a bigger file.
How do I fit a video under a size limit?
Lower the bitrate or resolution — the estimate shows the bitrate to target for a given length to stay under the cap.
Is anything uploaded?
No. The calculation happens in your browser.