What the number describes
A 10 Mbps video spends ten million bits on every second, on average. Across 60 seconds that is 600 million bits — 75 MB — which is why file size is simply bitrate × time ÷ 8. Encoders distribute those bits unevenly: simple scenes get fewer, busy scenes more, and the average lands on the target. The video file size calculator applies that formula to any duration and bitrate pair, and the video bitrate calculator runs it in reverse from a size target.
Quality depends on content and codec
Two videos at 8 Mbps are not equal: a static interview is pristine while a handheld shot of a crowd shows artefacts. Codecs shift the entire scale as well — H.265/HEVC reaches H.264 quality at about 40% fewer bits, and AV1 at roughly half, though encoding takes longer and older devices may not decode it in hardware.
Recommended bitrates
- 720p30: 2.5 Mbps · 720p60: 5 Mbps
- 1080p30: 5 Mbps · 1080p60: 8 Mbps
- 1440p60: 16 Mbps
- 4K30: 25 Mbps · 4K60: 45 Mbps
- Live streaming 1080p60: about 6 Mbps (Twitch recommends 6,000 kbps with an 8,500 kbps ceiling)
Variable, constant and quality-based encoding
CBR holds the bitrate steady, which many live platforms require. VBR spends more where needed and less elsewhere, giving better quality at the same average. CRF/CQ targets a quality level and lets the bitrate float — ideal for archives, where consistent quality matters more than a predictable size. For a fixed size limit, use two-pass VBR.