Free calculator
Video Bitrate Calculator
File size = bitrate × runtime ÷ 8. Enter a bitrate and a runtime to get the file size, a card or drive size to get the record time, or a target file size to get the bitrate that fits it, with the audio taken out.
Free, no sign-up. Runs in your browser.
This web tool applies drop-frame timecode in every mode, so the same runtime gives the same size whichever way you solve. Save, share and get the Pro tools in the app.
How it works
size (bytes) = bitrate (bit/s) × runtime (s) ÷ 8In everyday units: GB = Mbps × seconds ÷ 8,000. Every unit is decimal: 1 Mbps is 1,000,000 bits a second, 1 GB is 1,000,000,000 bytes and 1 TB is 1,000 GB. The bitrate is the whole file, video and audio together.
runtime (s) = size (bytes) × 8 ÷ bitrate (bit/s)A 1 TB drive holds 8,000,000 megabits, so its record time in seconds is 8,000,000 ÷ the bitrate in Mbps. Halve the bitrate and the record time doubles.
total bitrate = size × 8 ÷ runtime; video = total − audioUncompressed PCM audio runs at bit depth × sample rate × channels: 24 × 48,000 × 2 = 2,304,000 bit/s for 24-bit stereo. The video bitrate is what is left of the budget.
seconds = frames ÷ frame rateTimecode counts 24 frames a second at 23.976, so 01:00:00:00 is 86,400 frames and 86,400 ÷ 23.976 = 3,603.6 real seconds. At 29.97 drop-frame, 01:00:00;00 is 107,892 frames, exactly 3,600 seconds.
Where the preset rates come from
The ProRes presets are Apple's target data rates from the ProRes white paper (April 2022), at the raster and frame rate named in each preset. ProRes is variable bitrate: Apple gives a target per frame and says no frame exceeds it by more than about 10 percent, so plan storage with some headroom. The DNxHR presets come from Avid's published bytes per frame at 23.976 fps, converted to decimal megabits. For a camera's own recording formats, type the rate from its maker's specifications.
In Bitrate mode the closest preset is the one nearest the video bitrate, shown when it is within 15 percent.
Worked example
One hour of ProRes 422 HQ at UHD, 23.976 fps
- 01:00:00:00 at 23.976 = 86,400 frames ÷ 23.976 = 3,603.60 s
- ProRes 422 HQ, UHD 3840×2160 24p: 707 Mbps = 707,000,000 bit/s
- 707,000,000 × 3,603.60 s = 2,547,747,747,748 bits
- 2,547,747,747,748 ÷ 8 = 318,468,468,468 bytes
- 318,468,468,468 bytes ÷ 1,000,000,000 = 318.47 GB
An hour of 23.976 timecode in ProRes 422 HQ UHD is 318.47 GB: 5.30 GB a minute, 3.18 TB in a 10-hour shoot day.
Quick reference
ProRes at UHD 3840×2160 24p: an hour and a 1 TB drive
| Codec (Apple target rate) | One hour (3,600 s) | Record time on 1 TB |
|---|---|---|
| ProRes 422 Proxy (145 Mbps) | 65.25 GB | 15 h 19 min 32 s |
| ProRes 422 LT (328 Mbps) | 147.6 GB | 6 h 46 min 30 s |
| ProRes 422 (471 Mbps) | 211.95 GB | 4 h 43 min 5 s |
| ProRes 422 HQ (707 Mbps) | 318.15 GB | 3 h 8 min 35 s |
| ProRes 4444, no alpha (1061 Mbps) | 477.45 GB | 2 h 5 min 40 s |
| ProRes 4444 XQ, no alpha (1591 Mbps) | 715.95 GB | 1 h 23 min 48 s |
Save, share and get the Pro tools in the CineMath app
CineMath is a free download for iPhone, iPad and Mac, with this calculator built in. In version 1.3, coming soon to the App Store, CineMath Professional saves calculations to your history, shares them as links, and adds the Camera Database and Data Planning.
Questions
How do I calculate video bitrate?
Divide the file size in bits by the runtime in seconds. In megabits: Mbps = file size in MB × 8 ÷ seconds. A 10 GB file that runs one hour is 10,000 × 8 ÷ 3,600 = 22.22 Mbps. Take out the audio to get the video bitrate: with AAC stereo at 256 kbps, the video gets 21.97 Mbps.
How big is an hour of 4K ProRes?
At UHD 3840×2160 24p, Apple's target rates give 211.95 GB an hour for ProRes 422 (471 Mbps), 318.15 GB for ProRes 422 HQ (707 Mbps) and 715.95 GB for ProRes 4444 XQ (1591 Mbps). An hour of 23.976 timecode runs 3,603.6 seconds, so ProRes 422 HQ comes to 318.47 GB. ProRes is variable bitrate: real files land close to the target.
How long will a 1 TB drive record?
Divide 8,000,000 megabits by the bitrate in Mbps. At 707 Mbps (ProRes 422 HQ, UHD 24p) that is 11,315 seconds, 3 hours 8 minutes 35 seconds. At 220 Mbps (ProRes 422 HQ, 1920×1080 29.97p) it is 10 hours 6 minutes 4 seconds.
Is 1 TB 1,000 GB or 1,024 GB?
Drive capacities, and this calculator, use decimal units: 1 TB is 1,000 GB, or 1,000,000,000,000 bytes. Software that counts in binary units shows the same drive as about 931 GiB (10^12 ÷ 2^30 = 931.32), which is why a new drive looks smaller than its label.
How do I convert MB/s to Mbps?
Multiply by 8: 100 MB/s is 800 Mbps. Check which megabyte a table uses. Avid's DNxHR table lists DNxHR HQ at UHD 23.976 as 83.26 MB/s in binary megabytes, which is 83.26 × 1,048,576 × 8 ÷ 1,000,000 = 698.4 Mbps.
Does drop-frame timecode change the file size?
Yes, by 0.1%. At 29.97 fps, 01:00:00;00 drop-frame is 107,892 frames, exactly 3,600 seconds, while 01:00:00:00 non-drop is 108,000 frames, 3,603.6 seconds. At 220 Mbps that is 99 GB against 99.1 GB.