How Bitrate and File Size Relate
A video file's size depends on three things: duration, video bitrate and audio bitrate. Bitrate is the amount of data encoded per second (Mbps or kbps); the higher it is, the better the image but the larger the file. This tool answers two questions: how much space will the file take with your settings, or which bitrate should you pick to fit a target size.
The Formula
File size (bits) = (video Mbps + audio kbps) × duration (seconds). Divide by 8 for bytes, then by the right multiples for MB/GB. For example, a 5-minute clip at 8 Mbps video + 128 kbps audio ≈ 305 MB. If you leave audio blank, the tool assumes 128 kbps.
Which Bitrate to Choose?
- 1080p social: 8–12 Mbps usually gives balanced quality.
- 1080p high quality / YouTube: 12–20 Mbps.
- 4K: 35–60 Mbps is common.
- Instagram/TikTok upload: the platform re-compresses; going above 10–15 Mbps rarely helps.
Note
Results are estimates assuming constant bitrate (CBR). Variable bitrate (VBR), codec (H.264, H.265/HEVC, AV1) and container differences change the actual size. For ad films, product videos and social content, see our video production service. For aspect ratios, use our Aspect Ratio Calculator.