BRAW File Size Calculator
Blackmagic RAW data rates and file sizes for every constant bitrate setting, derived from the compression ratio Blackmagic publishes in its Blackmagic Design camera manual, with the derivation checked against the Blackmagic RAW data rate calculator and the check printed on this page.
Calculator
What this calculator is for
Blackmagic RAW is a camera format, so this page answers camera questions: how much card a setting eats, how fast the media has to be, and what changes when you move up a resolution or down a ratio.
- Before the shoot. You are choosing between 3:1 and 8:1, or between 6K and 4K, and you want to know what each choice costs in cards and in copy time.
- On the day. You need megabytes per second, because that is the number your card has to sustain. It is the headline result here for exactly that reason.
- In the edit. You are working out how much drive the project needs once the cards come off the camera, which is the same figure multiplied by hours and then by two.
- Comparing formats. You want BRAW and ProRes on one axis so the argument stops being about which sounds better. The table further down does that at UHD 24 fps.
Why this page shows its working
Apple publishes a table of ProRes data rates. Blackmagic does not publish an equivalent table for Blackmagic RAW. What Blackmagic publishes is the definition, and the definition is enough.
In the Blackmagic camera manual, the constant bitrate settings are explained as ratios between the uncompressed RAW file size and the file you get. Their example is direct: 12:1 compression produces a file about twelve times smaller than uncompressed RAW. So if you know the size of an uncompressed sensor frame, you know the compressed rate.
An uncompressed frame is width times height times the bit depth of each photosite. Blackmagic cinema cameras read out 12 bit RAW, so the arithmetic is:
Twelve bits is an assumption, and rather than bury it in the code this page puts it in the form as a field you can change. That is the difference between a derivation and a guess: a derivation tells you what it assumed.
The derivation, done by hand
Take 6K DCI, 6144 x 3240, at 24 frames per second, at 5:1.
One uncompressed frame is 6144 x 3240 photosites, which is 19,906,560 of them, times 12 bits each, which is 238,878,720 bits per frame. Twenty four of those a second is 5,733,089,280 bits per second uncompressed. Divide by the ratio of 5 and you have 1,146,617,856 bits per second, or 1,147 Mbps. Divide by 8 for bytes and you get 143.3 MB per second, and multiply that by 3,600 for 516 GB per hour.
Blackmagic's own calculator gives 141 MB/s for that setting. The derivation is 1.6 percent high, which is close enough to plan a shoot on and far enough away that this page shows you both numbers instead of hiding one.
What the ratio actually buys you
The ratios are linear, which makes the whole format easy to hold in your head. At any given resolution and frame rate, 3:1 is four times the data of 12:1, and 5:1 is exactly 2.4 times 12:1. So once you know one figure you know all four.
Resolution scales the same way, by photosite count rather than by name. 6K DCI at 6144 x 3240 has 19.9 million photosites. UHD at 3840 x 2160 has 8.3 million. That is a factor of 2.4, and the data rates differ by exactly that factor: 1,911 Mbps against 796 Mbps at 3:1 and 24 fps. This is why a 6K camera shot in UHD is not a compromise on storage, it is a completely different order of cost.
The check against Blackmagic
A derivation is only worth something if it survives contact with the publisher's own numbers. Blackmagic runs a data rate calculator on their product pages. These five figures were read from it for the Blackmagic Cinema Camera on 22 August 2026, and compared with what the formula above produces for the same settings.
| Setting | Blackmagic publishes | This site derives | Difference |
|---|
Under two percent on every one, in both directions, and the ratios scale exactly: the 3:1 rate is precisely four times the 12:1 rate in both Blackmagic's numbers and ours. There is one more agreement worth noting. Blackmagic's calculator says a 1 TB drive holds 1.2 hours at 6K DCI 24 fps 3:1. At their published 235 MB/s, one decimal terabyte lasts 4,255 seconds, which is 1.18 hours. Their calculator counts a terabyte as a thousand billion bytes, exactly as this site does.
Constant bitrate against constant quality
This is the part most BRAW calculators skip, and it is the part that decides whether the number on this page is useful to you.
Constant bitrate is 3:1, 5:1, 8:1 and 12:1. The codec holds the rate. If a frame needs more data than the allowance, it gets compressed harder. Predictable file size, quality that can move.
Constant quality is Q0, Q1, Q3 and Q5. These set how much quantization is applied and let the file grow to whatever the image needs. Blackmagic is explicit that in this mode you cannot tell what the file size ratio will be, because it varies with what you are shooting.
So this calculator does constant bitrate only, and will not offer you a Q0 number. Blackmagic does give one useful signpost in their manual: on the camera, the remaining time estimate for Q0 looks similar to 3:1, and Q5 looks similar to 12:1. Use those as the shape of the thing, then do what the manual actually recommends, which is to roll for twenty seconds and watch the estimate on the touchscreen. On a shoot that takes less time than reading this paragraph.
BRAW against ProRes, on the same axis
The comparison people actually want. UHD at 24 fps, every rate side by side, so the file size difference is visible without converting anything in your head. The ProRes figures are Apple's published rates and the BRAW figures are derived as described above.
| Format | Mbps | MB/s | GB per hour | Where the figure comes from |
|---|---|---|---|---|
| ProRes 4444 XQ | 1,591 | 198.9 | 716 | Apple published |
| ProRes 4444 | 1,061 | 132.6 | 477 | Apple published |
| Blackmagic RAW 3:1 | 796 | 99.5 | 358 | derived from the published ratio |
| ProRes 422 HQ | 707 | 88.4 | 318 | Apple published |
| Blackmagic RAW 5:1 | 478 | 59.7 | 215 | derived from the published ratio |
| ProRes 422 | 471 | 58.9 | 212 | Apple published |
| ProRes 422 LT | 328 | 41.0 | 148 | Apple published |
| Blackmagic RAW 8:1 | 299 | 37.3 | 134 | derived from the published ratio |
| Blackmagic RAW 12:1 | 199 | 24.9 | 90 | derived from the published ratio |
| ProRes 422 Proxy | 145 | 18.1 | 65 | Apple published |
What this table shows, once you sit with it, is that the argument between RAW and an intermediate codec is not always a storage argument. Blackmagic RAW at 12:1 costs less per hour than ProRes 422 HQ at the same size and rate, and it is still RAW, with the sensor data and the latitude that comes with it. At 3:1 it costs more than ProRes 4444. The setting matters more than the format name.
One warning that belongs on this page and not in a footnote. Blackmagic RAW writes a sidecar file next to the clip, and cameras write proxies and metadata too. None of it is large. All of it is real, and it lands on the same card.
Practical notes from a set
The rate that matters on the day is not gigabytes per hour, it is megabytes per second, because that is what the card has to sustain without dropping a frame. The calculator prints it as the headline for that reason. If your media cannot hold that number continuously, the shot fails, and it fails in the middle of the take rather than at the start.
Blackmagic's own manual is blunt about a related trap: some cards have slower write speeds than read speeds, and the box usually advertises the read speed. Check the write figure, and check it for sustained writing rather than a burst.
Five things that move the real number
Everything on this page is an estimate, and these are the specific reasons it will not match what the camera reports.
The bit depth assumption. Twelve bits per photosite is the number this page uses and it is the number in the field above. If your sensor reads out differently, change it and the whole result moves proportionally. Nothing is hidden.
Constant quality has no answer. Q0, Q1, Q3 and Q5 set how much quantization is applied and let the file grow to whatever the image needs. Blackmagic states there is no upper limit on the file size in that mode, and that you really cannot tell what the file size ratio will become. This calculator therefore offers constant bitrate only.
The frame rate may not be available. Data rate scales with frames per second, so it is tempting to compute 6K open gate at 60. The manual publishes maximum sensor frame rates that stop that: 36 for 6K open gate 3:2 at 6048 x 4032, 48 for 6K DCI 17:9, 60 for 6K 2.4:1 and for 4K DCI 17:9, 50 for Super 35 4:3, 100 for Super 16 16:9 and 120 for 1080 HD. Those are for the Blackmagic Cinema Camera, and other bodies differ, so read your own manual before you budget a rate the camera will not shoot.
The file system. Blackmagic notes that recording duration varies slightly between manufacturers and with whether the media is formatted exFAT or Mac OS Extended. It is a small effect, and it is real.
The direction of the error. This one is worth knowing because it runs the friendly way for once. Blackmagic states that the values in their record duration tables assume shots with high complexity, so you may get slightly longer record times than published. A calculator that estimates from the ratio, as this one does, is estimating the rate rather than the worst case, so treat the result as a middle figure and keep your own margin.
What to do when the number will not settle it
Blackmagic gives one piece of advice in the manual that is better than any calculator, and it costs twenty seconds. The remaining time estimate on the camera updates every ten seconds while recording, so record for twenty seconds in the exact setting you plan to use and watch the duration in the media area of the touchscreen. That figure comes from the camera, with your card, on your footage, and it beats every derived number on this page including mine.
Use this page to decide what to test. Use the camera to confirm it.
Common questions
What is the data rate of Blackmagic RAW 12:1?
It depends on the sensor readout and frame rate, because the ratio is measured against the uncompressed frame. At 6K DCI 6144 x 3240 and 24 fps, Blackmagic publish 59.0 MB/s for 12:1. The same ratio at UHD 24 fps works out much lower, because there are fewer photosites to compress.
Is BRAW smaller than ProRes?
It depends on the setting. At UHD 24 fps, Blackmagic RAW 12:1 costs less per hour than ProRes 422 HQ, while Blackmagic RAW 3:1 costs more than ProRes 4444. The compression setting matters more than the format name.
Why can nobody calculate a Q0 or Q5 file size?
Because constant quality has no fixed rate by design. Blackmagic states that in constant quality mode the file size ratio varies with what you are shooting. Their manual suggests recording for twenty seconds and watching the remaining time estimate on the camera.
Constant bitrate or constant quality, which should I shoot?
Blackmagic explains the trade in their own manual and it is a genuine trade. Constant bitrate holds the rate, so if an image needs more data the codec compresses harder to fit the allowance. Their warning about that is the useful part: it is possible to lose quality without knowing it until you get back from the shoot. Constant quality inverts it. The file grows to whatever the image needs, with no upper limit, which protects the picture and puts the risk on your media instead. Blackmagic notes that a file can grow beyond what the card can keep up with, and that this shows up as dropped frames. Predictable storage, or predictable quality. Pick which one you can afford to be surprised by that day.
What is the difference between Q0 and Q5?
They are different levels of quantization. Blackmagic describes Q5 as having a greater level of quantization but offering a greatly improved data rate, which in plain terms means smaller files and more compression. For rough planning, the manual gives one signpost: the on camera duration estimate for Q0 looks similar to constant bitrate 3:1, and Q5 looks similar to 12:1. Treat that as the shape of the thing rather than a number, because in constant quality mode there is no fixed ratio to calculate from.
How much Blackmagic RAW fits on a 1TB card?
At 6K DCI 6144 x 3240 and 24 fps, this derivation gives about 1 hour 10 minutes at 3:1, 1 hour 56 minutes at 5:1, 3 hours 6 minutes at 8:1 and 4 hours 39 minutes at 12:1. Blackmagic's own calculator says 1.2 hours for 6K DCI 3:1, which lines up with the 3:1 figure and also confirms that they count a terabyte as a thousand billion bytes, the same way this site does.
How big is Blackmagic RAW at 4K?
Smaller than most people expect, because the photosite count falls fast. At UHD 3840 x 2160 and 24 fps, the derivation gives 796 Mbps at 3:1, which is 358 GB an hour, and 199 Mbps at 12:1, which is 90 GB an hour. At 4K DCI 4096 x 2160 and 24 fps, 3:1 is 849 Mbps and Blackmagic publishes 108 MB/s for it, which is 864 Mbps. Two independent routes, under two percent apart.
Is 12:1 too compressed to use?
Blackmagic themselves say in the manual that many users of Blackmagic RAW find 12:1 has been perfectly acceptable and have not seen quality limitations, and then add the only sensible next sentence, which is that it is best to experiment and try various settings for yourself. Shoot your hardest scene at 12:1 and at 5:1, grade both as hard as the job will need, and look at them. That test takes an afternoon once and settles the question for every job afterwards.
How do I open a BRAW file on Windows?
Blackmagic ships a Blackmagic RAW Player in the camera software installer, and the manual states it is available for Mac, Windows and Linux. DaVinci Resolve reads the format directly on all three as well, and the sidecar file that sits next to the clip is human readable, so the settings a camera or a colourist applied can be inspected in a text editor. That last part matters more than it sounds: if a clip is opening with the wrong look, the sidecar is the first thing to check.
How does Blackmagic RAW compare with ProRes RAW for file size?
There is no honest table for that comparison, and any page showing you one has made it up. Blackmagic publishes the ratio their format uses, which is why the rates on this page can be derived and checked. Apple does not publish target data rates for ProRes RAW, because it is variable by design. So the only reliable comparison is the one you measure: shoot the same scene on both, look at the files, and use the storage calculator with the numbers you got.