Video data rate
calculator.
Pick a codec, resolution and frame rate — or type the bitrate your camera records — and see the data rate, the storage per hour, and how long a card or drive will last.
ProRes figures scale Apple's published target rates by pixel count and frame rate. ProRes is variable bitrate, so real files land a little above or below. Storage is in decimal GB, as card makers label them; the formatted space on a card is slightly smaller.
How to calculate video file size
A video's data rate is how many bits it writes every second. Everything else follows from it:
- Megabytes per second = Mb/s ÷ 8 (there are 8 bits in a byte).
- Gigabytes per hour = Mb/s × 3,600 ÷ 8 ÷ 1,000.
- Recording time on a card = card size in GB × 8,000 ÷ Mb/s, in seconds.
For a camera codec like H.264, H.265/HEVC or XAVC, the bitrate is printed in the recording menu (for example "100 Mbps") — choose Other codec and type it in. Apple ProRes is defined by a target rate per flavour at 1920 × 1080 and 29.97 fps, which grows in step with the number of pixels and frames:
| ProRes flavour | 1080p 29.97 | UHD 23.976 | UHD GB / hour |
|---|---|---|---|
| 422 Proxy | 45 Mb/s | ≈144 Mb/s | ≈65 GB |
| 422 LT | 102 Mb/s | ≈326 Mb/s | ≈147 GB |
| 422 | 147 Mb/s | ≈470 Mb/s | ≈212 GB |
| 422 HQ | 220 Mb/s | ≈704 Mb/s | ≈317 GB |
| 4444 | 330 Mb/s | ≈1,056 Mb/s | ≈475 GB |
| 4444 XQ | 500 Mb/s | ≈1,600 Mb/s | ≈720 GB |
Worked example
A two-camera day in ProRes 422 HQ, UHD at 23.976 fps. UHD has four times the pixels of 1080p and
23.976 is 0.8 of 29.97, so the rate is 220 × 4 × 0.8 ≈ 704 Mb/s, or 88 MB/s. That is
about 317 GB per hour per camera. With two hours of rolling per camera, the day
produces about 1.27 TB of original media — before you make a second copy, which you always
should. A 512 GB card holds roughly 1 hour 37 minutes of it.
Knowing the GB per hour tells you how many cards to carry, how big the shuttle drives must be, and how long an offload will take. If you offload on set, see checksum-verified card offload for why every copy should be verified.
Keep the camera math on set.
Set Math bundles card runtime, exposure and more calculators, free, on iPhone and iPad — no signal needed. Also try the film footage calculator for celluloid.
Data rates, answered.
What is the difference between Mb/s and MB/s?
Mb/s is megabits per second, the unit codecs and cameras use. MB/s is megabytes per second, the unit drives and card readers use. Divide Mb/s by 8 to get MB/s: 704 Mb/s is 88 MB/s.
How many GB is an hour of 4K footage?
It depends entirely on the codec. UHD at 23.976 fps is about 65 GB per hour in ProRes 422 Proxy, about 317 GB in ProRes 422 HQ, and about 45 GB in a 100 Mb/s H.265 recording.
Does frame rate change the file size?
For ProRes, yes — the rate scales with frames per second, so 59.94 fps is about 2.5 times the size of 23.976. Many long-GOP camera codecs instead record a fixed bitrate you choose in the menu, whatever the frame rate.
Why is my card smaller than its label?
Card makers count 1 GB as 1,000,000,000 bytes, while computers often report in binary units, and formatting reserves some space. Plan on a few percent less than the label.