Video Bitrate Time Size Calculator

Video file size: bitrate times duration

A video stream follows the same rule as everything else: size = bitrate · duration. An hour of H.264 1080p at 8 Mbps comes out to (8 · 3600) / 8 ≈ 3.6 GB. Newer codecs shave that down a lot. H.265 (HEVC) matches the quality at about half the bitrate, and AV1 goes another ~30% leaner than HEVC. The container itself (MP4, MKV) tacks on 1–3% of overhead. For a longer recording, take the average bitrate, multiply by the total seconds, and divide by 8 to turn bits into bytes.

Applications: storage planning and OTT ladders

Editors size their NVMe/SSD scratch disks around raw and proxy bitrates. OTT services like Netflix and Disney+ publish bitrate ladders (1080p at 5 Mbps, 4K HDR at 15 Mbps, and so on) so the player can grab the right rendition for whatever bandwidth the viewer has. And YouTube uploaders like to work out the archival size before they ever hit export.

FAQ

How much does HEVC really save? Roughly 40–50% smaller files than H.264 at the same perceived quality. The catch is that it leans harder on the CPU and GPU, both when encoding and when playing back.

Does resolution alone determine size? No, the bitrate is what does it. A badly encoded 4K can end up smaller than a 1080p running at a high bitrate.

Is the result exact? Treat it as an estimate of the video track alone. Audio, subtitles, and container overhead each add a small slice on top.