How the bitrate is calculated
A modern bitrate target is driven by the number of pixels per second the codec has to compress, scaled by how efficient that codec is and how much motion is in the picture:
bitrate_kbps = (width × height × fps × bits_per_pixel) × motion_factor × hdr_factor ÷ 1000
Where bits_per_pixel is a codec-efficiency constant: 0.10 for H.264, 0.05 for HEVC, 0.035 for AV1, and 0.06 for VP9. motion_factor ranges from 0.75 for low-motion content (talking heads, news) to 1.4 for high-motion (sports, gaming). HDR adds about 25% on top of SDR.
Worked example - 1080p30 H.264 standard motion, SDR
(1920 × 1080 × 30 × 0.10) × 1.0 × 1.0 / 1000 = 6,221 kbps ≈ 6.2 Mbps - which matches the table below and the YouTube / Apple HLS authoring guidance for 1080p30.
Recommended bitrate reference (H.264, SDR, standard motion)
| Resolution | 30 fps | 60 fps | HEVC equivalent (30 fps) |
|---|---|---|---|
| 360p (640×360) | 0.7-1.0 Mbps | 1.2-1.5 Mbps | 0.35-0.5 Mbps |
| 480p (854×480) | 1.0-1.5 Mbps | 1.8-2.5 Mbps | 0.5-0.75 Mbps |
| 720p (1280×720) | 2.5-4 Mbps | 4-6 Mbps | 1.25-2 Mbps |
| 1080p (1920×1080) | 5-8 Mbps | 8-12 Mbps | 2.5-4 Mbps |
| 1440p (2560×1440) | 9-14 Mbps | 14-20 Mbps | 4.5-7 Mbps |
| 4K (3840×2160) | 20-30 Mbps | 35-50 Mbps | 10-18 Mbps |
| 8K (7680×4320) | 50-80 Mbps | 80-120 Mbps | 25-45 Mbps |
For AV1, take about 70% of the HEVC value. For VP9, take about 120% of the HEVC value. Live sports needs the high end of each range; talking-head content lives at the low end.
Calculating file size
Once you have a target bitrate, the file size for a known duration is straightforward:
file_size_MB = bitrate_Mbps × duration_seconds / 8
A 60-minute 1080p H.264 file at 6 Mbps occupies roughly 6 × 3,600 / 8 = 2,700 MB ≈ 2.7 GB. The calculator above adds audio overhead and gives a 20% delivery-bandwidth buffer so a CDN sees realistic peak rates instead of average ones.
Frequently Asked Questions
What is a good bitrate for 1080p streaming?
For 1080p at 30 fps using H.264, a target bitrate of 5-8 Mbps produces good quality for most content. For 1080p at 60 fps, target 8-12 Mbps. With HEVC, halve those targets; with AV1, take roughly one-third.
What bitrate should I use for 4K streaming?
For 4K (2160p) at 30 fps in H.264, target 20-30 Mbps. At 60 fps, target 35-50 Mbps. HEVC roughly halves these (around 15-25 Mbps for 4K60); AV1 reduces further to 10-18 Mbps.
How do I calculate file size from bitrate?
File size in megabytes equals bitrate in Mbps multiplied by duration in seconds, divided by 8. A 90-minute 1080p H.264 file at 6 Mbps is roughly (6 × 5,400) / 8 = 4,050 MB ≈ 4 GB.
How much bitrate does HEVC save over H.264?
HEVC (H.265) typically delivers similar visual quality at 40-50% of the bitrate of H.264. AV1 saves a further 20-30% over HEVC, at the cost of significantly higher encode time.
What bitrate does Roku and Fire TV support?
Roku and Fire TV both support up to 4K HDR streams in HEVC and H.264. Most CTV publishers target around 6 Mbps for 1080p and 15-25 Mbps for 4K HEVC to balance quality with CDN egress cost.