SHEET 04 · Data rates
Bitrate and data volume tables
Reference tables of stored data volume per hour for 1080p, 4K and 8K pictures at several constant bitrates, with a short guide to reading them.
What the tables state
A bitrate is a rate of flow, expressed in bits per second. A data volume is an amount, expressed in bytes or in gigabytes. The two are linked by time: an hour of material at a constant bitrate occupies a predictable volume. The tables below give that volume for the three picture sizes most often discussed in engineering work. Each row is a constant bitrate; each figure is the volume of one hour of video at that rate.
Two conventions must be declared before any such table is read. First, these tables use decimal units, so one gigabyte is one thousand megabytes and one megabyte is eight million bits. Second, they describe video payload only. A real recording also carries audio, system data and file overhead, so the total sought in practice will be slightly larger than the figure shown. The difference is small but should not be forgotten when planning storage.
Volume per hour at 1080p
| Bitrate (Mbit/s) | Volume per hour (GB) | Volume per 10 hours (GB) |
|---|---|---|
| 8 | 3.6 | 36 |
| 12 | 5.4 | 54 |
| 16 | 7.2 | 72 |
| 24 | 10.8 | 108 |
Volume per hour at 4K
| Bitrate (Mbit/s) | Volume per hour (GB) | Volume per 10 hours (GB) |
|---|---|---|
| 25 | 11.25 | 112.5 |
| 40 | 18 | 180 |
| 60 | 27 | 270 |
| 80 | 36 | 360 |
Volume per hour at 8K
| Bitrate (Mbit/s) | Volume per hour (GB) | Volume per 10 hours (GB) |
|---|---|---|
| 80 | 36 | 360 |
| 120 | 54 | 540 |
| 160 | 72 | 720 |
| 240 | 108 | 1080 |
How to read the tables
Start from the bitrate you intend to hold, not from the picture size. The picture size decides how many bits are needed to reach a given quality, but the bitrate is what the channel or the medium must actually carry. Find the row for your bitrate, read across, and the volume per hour is the figure you need. For a different duration, multiply: two hours is twice the figure, fifteen minutes is a quarter of it.
It is worth noticing how quickly the volume grows with picture size. A 4K picture has four times the pixels of a 1080p picture, and at the same quality target it needs roughly two to three times the bitrate, because the newer coding standards describe the larger picture more efficiently. An 8K picture has sixteen times the pixels of 1080p, and its bitrate demand is correspondingly greater, although the exact ratio again depends on the coding standard and on the content.
Plate 8 — volume of one hour of video at five representative operating points. The bars show how volume tracks the bitrate directly.
Using the tables in planning
These figures are the arithmetic floor for any storage or carriage plan. A day of continuous 4K recording at forty megabits per second occupies about 432 gigabytes, and a week occupies roughly three terabytes. A transport that must carry eight such channels simultaneously needs a sustained rate of three hundred and twenty megabits per second. The tables make those multiplication steps immediate, and they also expose the cases where the assumption of a constant bitrate breaks down: for variable-rate material the average is the quantity to use, but the peak decides the buffer and the link.