I have a 64GB SD card in my Canon Vixia HF G30, and at 1920x1080/60P/28Mbps it can hold just over 7 and a half hours of video. A 32GB card will hold half that (3h 19m) and 16GB would hold about an hour and 40 minutes.

Make sure you get a Class 10 SD(XC) card to handle the data rate. I'm using a SanDisk Extreme which is rated at 45Mbps.

YouTube/optodata

DS365 | Win11 Pro | Ryzen 9 3950X | RTX 4070 Ti | 32GB RAM | 10TB SSDs | 5K+4K HDR monitors

Canon Vixia GX10 (4K 60p) | HF G30 (HD 60p) | Yi Action+ 4K | 360Fly 4K 360°

Canon camera shooting 1920x1080i @ 17 Mbps = 1hr03 min on a 8GB SD card. 2 hours 6 min about on 16 GB card.

Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.

Actually the question implied the answer: 28 Mbit/s = 3.5 MiB/s = 12,600 MiB/hour. One hour of video will be around 12.3 gigabytes at that rate.
That said, different cameras encode video at different rates. If you aren't sure if the rate is 28 Mbit/s, you could record a minute of video with your camera and look at the file size. I.e. multiply it by 60 to get the size for one hour.
Be aware that SD cards are usually formatted with the ancient FAT32 file system, which has a file size limit of 4 GiB. At 28 Mbit/s you wont be able to record even 20 minutes in one go to that file system. Depending on the camera it might stop recording or loose a fraction of a second when it opens another file to continue recording.

Quote: Actually the question implied the answer: 28 Mbit/s = 3.5 MiB/s = 12,600 MiB/hour. One hour of video will be around 12.3 gigabytes at that rate.
That said, different cameras encode video at different rates. If you aren't sure if the rate is 28 Mbit/s, you could record a minute of video with your camera and look at the file size. I.e. multiply it by 60 to get the size for one hour.
Be aware that SD cards are usually formatted with the ancient FAT32 file system, which has a file size limit of 4 GiB. At 28 Mbit/s you wont be able to record even 20 minutes in one go to that file system. Depending on the camera it might stop recording or loose a fraction of a second when it opens another file to continue recording.

This (what mleise said)... and try to see if the camera supports exFAT. If it does, simply format the card with exFAT using the camera and then you can create files up to 16 Exabytes (about 17 Billion Gigabytes) in size, if the SD card is large enough and you want to have a recording that long of something "special".


'Video Size' Tip:
Bitrate dictates how much space the video file is going to take up. Nothing else.

Resolution ("size") doesn't matter, fps (frames per second) doesn't matter, the codec used doesn't matter - nothing else matters when it comes to output filesize - the only thing that dictates how big a file is going to be in the end is the bitrate used.
[Higher settings (resolution, fps, etc) will look better with a higher bitrate, of course]

Simply find out what your camera is using for bitrate and you can calculate how much space (or time) you can film for
[assuming CBR (Constant BitRate)... there is way to much about VBR and how it can affect filesize to write here, but you can guesstimate how much space it is going to take up, usually from references/examples given in the manual for your camera]

Quote: 'Video Size' Tip:
Bitrate dictates how much space the video file is going to take up. Nothing else.

Resolution ("size") doesn't matter, fps (frames per second) doesn't matter, the codec used doesn't matter - nothing else matters when it comes to output filesize - the only thing that dictates how big a file is going to be in the end is the bitrate used.
[Higher settings (resolution, fps, etc) will look better with a higher bitrate, of course]

Simply find out what your camera is using for bitrate and you can calculate how much space (or time) you can film for
[assuming CBR (Constant BitRate)... there is way to much about VBR and how it can affect filesize to write here, but you can guesstimate how much space it is going to take up, usually from references/examples given in the manual for your camera]

Bit Rate is not the only contributor to file size.

http://archive.today/8Gvov

Bit rate is the largest factor in file size, but not the only parameter.
Resolution plays a good part as does frame rate.

If nothing else is changed, then Bit Rate is the main factor.

Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.

Quote: Bit Rate is not the only contributor to file size.

http://archive.today/8Gvov

Bit rate is the largest factor in file size, but not the only parameter.
Resolution plays a good part as does frame rate.

If nothing else is changed, then Bit Rate is the main factor.

No, Troy was correct here. If an overall bit rate for the stream is given it means exactly that: A video produced by this camera takes up X MBit/s on average. If at the same bit rate you change FPS or resolution, the file size will be unaffected, but the quality will change.
A fixed rate makes two assumptions:
1) The recording or playback device (SD card, DVD, network, ...) has a guaranteed sustained transfer rate of X MBit/s.
2) The playback device has X megabytes of memory that acts as a buffer to hold frames not yet played back.
For example, for a video blu-ray disk the rate has been defined to be 53,95 Mbit/s.

The video encoder now has to think ahead: It needs to make sure that the buffer doesn't run out of video frames to display, which can happen if they are too large to be transferred into the buffer in time at the give bit rate. On the up side it can write many small frames into the buffer ahead of time. E.g. a lot of highly compressed frames take their time to display, but are quick to transfer. This buys some time for a larger video frame. (Note: This results in two time stamps for a video frame: the presentation or display time and the time the frame appears in the stream at the fixed MBit/s.)

When offline converting videos at fixed bit rates, this is sometimes combined with 2-pass encoding. The first pass will analyze the video in relation to the target bit rate and buffer size to make best use of the buffer to achieve good quality. This requires looking ahead to see if following video frames may require more buffer space and the current frame thus needs to be compressed stronger. Where this is not possible, i.e. in live stream conversion you often get horrible blocking artifacts on fixed rate streams like TV broadcasts with a sudden change of scene.