You shot 30 minutes of 4K video on your iPhone. Your friend shot the same scene on a Canon mirrorless. Your card shows 8 GB used; theirs shows 80. Both are "4K" — but they encoded at very different bitrates. Here's what determines actual file size and what to expect for various 4K use cases.
The basic math
Video file size = bitrate × duration / 8.
- Bitrate is in megabits per second (Mbps).
- Duration in seconds.
- Divide by 8 to convert bits to bytes.
For example: 25 Mbps × 60 seconds ÷ 8 = 187.5 MB per minute.
Common 4K bitrates
| Source | Bitrate | 1 minute size | 1 hour size |
|---|---|---|---|
| YouTube 4K (compressed) | 15–25 Mbps | 112–187 MB | 6.7–11 GB |
| Netflix 4K | 15–25 Mbps | 112–187 MB | 6.7–11 GB |
| Apple TV 4K (HEVC) | 40 Mbps | 300 MB | 18 GB |
| Blu-ray 4K UHD | 50–100 Mbps | 375–750 MB | 22–45 GB |
| iPhone 4K (HEVC) | 50 Mbps | 375 MB | 22 GB |
| Canon R5 4K (compressed) | 120–340 Mbps | 900 MB–2.5 GB | 54–150 GB |
| RED RAW | 500–1000+ Mbps | 3.7–7.5 GB | 225–450 GB |
Why such variation
The same "4K" can be encoded at any bitrate. Lower = smaller files but more compression artifacts. Higher = larger files but more detail preserved.
The encoder also matters:
- H.264: older codec, higher bitrates needed for similar quality.
- H.265 / HEVC: ~50% more efficient than H.264. Same quality at half the bitrate.
- AV1: ~30% more efficient than HEVC. Slow to encode but excellent quality per byte.
- VP9: Google's codec, between HEVC and AV1.
Streaming vs recording
Streaming services (Netflix, YouTube) use heavily compressed video. They optimize for bandwidth — viewers don't notice modest quality losses on a TV. 4K Netflix at 15 Mbps looks fine on most screens.
Recording (smartphone, camera) uses higher bitrates. The recorded file will be edited or transcoded later, so you want preservation.
The same 30-minute 4K Netflix episode (~3 GB) is much smaller than 30 minutes of 4K iPhone footage (~10 GB) because of bitrate.
4K resolution vs bitrate
Don't confuse resolution and bitrate:
- Resolution: 3840×2160 pixels (about 4K).
- Bitrate: how much data per second to encode those pixels.
Higher bitrate at the same resolution = better quality, larger files. Lower bitrate at higher resolution can look worse than higher bitrate at lower resolution.
For most viewers, 1080p at 10 Mbps looks better than 4K at 5 Mbps. The "more pixels" advantage is wasted on aggressive compression.
Storage planning by use case
iPhone 4K recording: ~50 Mbps HEVC. 22 GB per hour of 4K video. A 256 GB iPhone with mostly photos and videos can hold ~10 hours of 4K.
YouTube creator workflow: shooting at 4K 100+ Mbps. 1 hour = 50 GB. A typical project (2 hours of footage cut to 15 minutes) needs ~100 GB while editing.
Family video archive: store at original bitrate or transcode to HEVC. 10 hours of 4K = 200–400 GB depending on choices.
Pro cinematographer: RED RAW at 500 Mbps+. 1 hour = 200 GB. Project workflow needs multi-TB storage.
HDR considerations
HDR (High Dynamic Range) video uses 10-bit color (vs SDR's 8-bit). The bitrate increase is modest — about 25% more data — but the visual difference is significant.
4K HDR streaming: ~25 Mbps (vs SDR's 15–20).
4K HDR recording: typically same as SDR but with extra metadata. iPhone 4K Dolby Vision HDR is ~100 Mbps.
Compression efficiency
Modern compression is impressive. AV1 4K at 8 Mbps can look as good as H.264 4K at 25 Mbps. As streaming services shift to AV1 (YouTube, Netflix), files get smaller for the same quality.
For end-users, this means 4K bandwidth requirements are slowly decreasing. 25 Mbps used to be the floor; 15 Mbps with AV1 is fine.
How long is 1 TB of 4K video?
| Source | Hours per 1 TB |
|---|---|
| YouTube 4K (15 Mbps) | ~150 hours |
| iPhone 4K (50 Mbps) | ~45 hours |
| Pro 4K (100 Mbps) | ~22 hours |
| RED RAW (500 Mbps) | ~4.5 hours |
A 1 TB drive holds anywhere from 4.5 hours to 150 hours of 4K depending on source.
Compressing existing 4K footage
If your 4K footage is too large:
- Re-encode with HEVC at 30–50 Mbps. Half the size, similar quality.
- Re-encode with AV1 if your editing software supports it. ~30% smaller than HEVC.
- Drop to 1080p if 4K isn't essential. ~25% the size.
Tools: HandBrake (free), FFmpeg (free, command-line), Adobe Media Encoder (paid), DaVinci Resolve (free for personal).
Estimate file size
Our file size estimator takes resolution, duration, and quality and returns estimated file size. Useful for planning storage capacity for video projects, or for budgeting upload bandwidth.